Transcript

Student Guide

Noise, Vibration, and HarshnessNVH

SAFETY NOTICE

warnings cautions notes

warnings cautions

Notes

Cautions warnings

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Noise, Vibration, and Harshness i

TABLE OF CONTENTSINTRODUCTION 1

OBJECTIVES 1

ACRONYMS 2

LESSON 1 EVALUATING NVH CONCERNS 5PRELIMINARY INFORMATION 5

Pre-road Test Inspection 7

Vehicle Road Test 8

Road Test Methods 9

Diagnostic Worksheet Page 1 10

Diagnostic Worksheet Page 2 11

LESSON 2 DIAGNOSING WHEEL AND TIRE VIBRATION 13WHEELS AND TIRES 13

NVH TERMS AND THEORY 14

Vibration Order 15

Cycle 16

Frequency 17

Amplitude 18

Resonance 19

NVH MEASURING TOOLS 20

Sirometer 20

Electronic Vibration Analyzer (EVA) 21

MTS 4100 22

ROAD TESTING FOR RESULTS 23

Slow Acceleration Test 23

Neutral Coast Down Speed Test 23

Calculating Wheel and Tire Frequency 24

Frequency Related Component Group 25

Wheel and Tire Balance 26

Radial Force 27

Radial Force Variation 28

MEASURING WHEEL AND TIRE RUNOUT 29

System Radial Runout 30

Radial Runout 31

Lateral Tire Runout 32

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Road Testing 36

ii Noise, Vibration, and Harshness

Slow Acceleration and Neutral Coast Down 36

Driveline Vibrations 37

Propeller Shafts 38

Propeller Shaft Runout 39

Calculating the Propeller Shaft Frequency 40

Driveline Operating Angles 42

Propeller Shaft Operating Angle 43

Measuring Operating Angles 44

Transmission Yoke Measurement 45

Propeller Shaft Measurement 46

Pinion Flange Measurement 47

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Engine-Speed Vibration 48

Engine Frequency Formula 49

First- and Second-order Engine Vibration 50

First-order Vibration 50

Torque Converter 50

Second-order Vibration 51

Half-order Engine Vibration 51

Engine Firing Frequency 51

Compelling Force of Exhaust 52

Engine Accessory Vibration 53

Calculating Engine Accessory Frequency 54

LESSON 4 DIAGNOSING NOISE 57GENERATION OF NOISE 57

Droning Noise 57

Tire Noise 58

Differential Noise 59

Growl Noise 60

Howl Noise 61

Road Testing 62

Telegraphing 63

Using the ChassisEAR 64

Attaching the Sensors 65

LESSON 5 HARSHNESS 67HARSHNESS 67

Suspension Components 67

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Noise, Vibration, and Harshness iii

GLOSSARY 71

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ROAD TEST METHODS 76

Road Test Tips 76

ROAD TESTING 76

Slow Acceleration Test 77

Neutral Coast Down Speed Test 77

Downshift Speed Test 77

Torque Converter Test 78

Steering Input Test 1 78

Steering Input Test 2 78

Neutral Run-up Test 79

Engine Loaded Test 79

Engine Accessory Test 80

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Engine-speed Frequency 84

Engine Frequency 84

Engine Accessory Frequency 84

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Vehicle Speed Frequency 85

Tire and Wheel Group 85

Propeller Shaft Group 86

Propeller Shaft Balancing 87

COMPLETE FORMULAS 88

Engine Vibration Formula 88

Engine Accessory Formula 88

Engine Firing Frequency Formula 88

Propeller Shaft Frequency Formula 88

SHORT FORMULAS 89

Engine Vibration Formula 89

Engine Accessory Formula 89

Engine Firing Frequency Formula 89

Propeller Shaft Frequency Formula 89

iv Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 1

INTRODUCTION

This training course focuses on how to use a systematic approach to diagnose and repair the root

cause of vehicle noise, vibration, and harshness (NVH) concerns.

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problems to certain component groups. This course also provides the ability to apply the theory of

NVH to isolate a component as the cause.

The primary sources of NVH concerns are generated by the following component groups:

=� Tire and wheel

=� Driveline

=� Engine and torque converter

OBJECTIVES

Upon completion of this course, you will be able to:

=� Perform a pre-road test inspection

=� Identify road test methods

=� Identify NVH diagnostic tools

=� Apply diagnostic methods

=� Classify the symptoms of NVH concerns

=� Calculate component frequencies

=� ������>?����'�%���%�%�/'������

=� Troubleshoot and repair NVH concerns

=� Diagnose and repair wheel and tire vibrations

=� Diagnose and repair driveline-related vibrations

=� Diagnose and repair engine-related vibrations

2 Noise, Vibration, and Harshness

ACRONYMS

The following is a list of acronyms used throughout this publication:

=� ABS Anti-lock Brake System

=� AC Alternating Current

=� CPS Cycle per Second

=� CV Constant Velocity

=� DRBIII Diagnostic Readout Box Third Generation

=� DTC Diagnostic Trouble Code

=� EVA Electronic Vibration Analyzer

=� Hz Hertz

=� NVH Noise, Vibration, and Harshness

=� RFV Radial Force Variation

=� RPM Revolutions per Minute

=� SAE Society of Automotive Engineers

=� SB Service Bulletin

Noise, Vibration, and Harshness 3

Notes:

4 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 5

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LESSON 1 EVALUATING NVH CONCERNS

PRELIMINARY INFORMATION

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Vehicle Road Test

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Road Test Methods

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Note: Detailed instructions for these road tests are provided in the Appendix.

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Noise, Vibration, and Harshness 13

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LESSON 2 DIAGNOSING WHEEL AND TIRE VIBRATION

WHEELS AND TIRES

Wheel-and tire-related vibrations occur at a relatively low frequency, typically 10–15 Hz. This can

result in a vibration experienced at speeds usually above 40 mph. Even a small amount of wheel

imbalance can translate into a vibration problem.

Tires wear faster than other components; as a result customers frequently replace original tires

with different types and sizes. When the tires are replaced, the wrong tire might be selected.

Some of the contributing factors to wheel and tire vibration can be:

=� Quality

=� Excessive runout

=� Non-uniformity

There are many sources of wheel and tire vibration some of the major sources are:

=� Wheel and tire imbalance

=� Condition of the wheels and tires

=� Foreign debris in wheel

=� Uniformity

=� Tire dimensions

=� Conicity

=� Radial force variation

=� Brake rotor

=� Constant velocity (CV) shaft

=� Hub

14 Noise, Vibration, and Harshness

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NVH TERMS AND THEORY

When diagnosing a vehicle with a vibration concern, you must be able to obtain the frequency

of the vibration. Diagnostic equipment is necessary to diagnose and repair NVH concerns. A

technician must be able to measure the frequency of the vibration, and relate the frequency of a

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In addition to using the diagnostic equipment, it is important that a technician clearly recognize

NVH theory and how it can be applied to identify the cause of a customer concern.

There are common characteristics of noise and vibration used to diagnose NVH concerns. The

following terms and graphics help explain how the frequency of a noise or vibration is used to

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=� Order

=� Cycle

=� Frequency

=� Amplitude

=� Resonance

– Source

– Transfer path

– Responder

Noise, Vibration, and Harshness 15

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1 First-order Vibration

(One Disturbance per Revolution)

2 Second-order Vibration

(Two Disturbances per Revolution)

Figure 4 Vibration Order

Order is the number of disturbances created in one revolution of a component. A single high spot

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disturbance of 10 Hz.

If the tire developed a second high spot, a second-order disturbance would result. The wheel

rotating 10 times per second produces 20 disturbances per second. This creates a second-order

disturbance of 20 Hz. Three high spots create a third-order disturbance and four high spots create

a fourth-order disturbance. Higher order disturbances continue to progress in this way.

Knowing the order can help you during troubleshooting. For example, a vehicle has a concern that

is producing a vibration at 20 Hz. After calculating wheel and tire frequency, it is determined that

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second-order frequency of the wheel and tire component group is 20 Hz.

16 Noise, Vibration, and Harshness

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1 Cycle 2 Cycles 3 Cycles

1 Second

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Figure 5 Cycle

Cycle is the path a wave travels before the wave begins to repeat the path again. If an AC sine

wave begins a path at zero volts, the wave completes one cycle when it returns to zero volts from

a positive voltage. In other words, the wave completes one cycle by traveling the path from a

negative voltage to zero volts, then to a positive voltage, and then back to zero volts.

If the wheel and tire makes three complete revolutions in one second, this is equal to three

complete cycles in one second.

Noise, Vibration, and Harshness 17

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1 Second

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Figure 6 Frequency

Frequency is the number of complete cycles that occur in one second. Sound and vibration waves

are measured in hertz (Hz), or cycles per second (CPS). One Hz is equal to one cycle per second.

The sound wave shown in the illustration below has a frequency of 6 Hz because it completes six

CPS. The frequency of a sound or vibration can aid in troubleshooting an NVH concern because

the frequency of the noise or vibration can be directly related to a component.

18 Noise, Vibration, and Harshness

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LowAmplitude

HighAmplitude

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Figure 7 Amplitude

Amplitude refers to the vertical measurement between the top and the bottom of a wave. Two

waves can have the same frequency, but differ in amplitude. Amplitude is the quantity or amount

of energy produced by a vibrating component. Amplitude determines how loud a noise is, or how

strong a vibration is.

Noise, Vibration, and Harshness 19

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1 Transfer Path 5 Compelling Force

2 Responder 6 Suspension Frequency

3 Source 7 Point of Resonance

4 Vibration Speed

Figure 8 Resonance

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Resonance is the tendency of a system to respond to a compelling force oscillating at, or near, the

natural frequency of the system. All objects have natural frequencies and experience maximum

response at the point of resonance.

The natural frequency of a typical automotive front suspension is in the 10–15 Hz range. This

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frequency is the same no matter what the vehicle speed. As the tire speed increases, along with

the vehicle speed, the disturbance created by the unbalanced tire increases in frequency.

Eventually, the frequency of the unbalanced tire intersects with the natural frequency of the

suspension, causing the suspension to vibrate. This intersection point is called the point of

resonance.

20 Noise, Vibration, and Harshness

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NVH MEASURING TOOLS

A technician must be able to use diagnostic equipment in order to measure the frequency of

a noise or vibration. A sirometer and several electronic tools are available for measuring and

recording noises and vibrations. Some of these tools have multiple vibration and noise inputs, as

well as recording and graphing capabilities.

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Figure 9 Sirometer

The sirometer is a tool that is useful when diagnosing NVH concerns. Originally used for reading

small engine rpm, this inexpensive tool is highly accurate for measuring vibration frequencies.

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frequencies. The tool can be purchased at most full service small engine repair and parts centers.

The sirometer has a wire that, when adjusted to the proper length, will vibrate at the same

frequency. To use the sirometer, hold it against a vibrating component. Rotate the dial to extend

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read the frequency on the face of the tool.

Always adjust the length of the wire from its smallest length to its longest length to ensure all

frequencies are being recorded. It is possible to have more than one vibration present in a vehicle.

Noise, Vibration, and Harshness 21

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1 12V Power Extension 6 EVA

2 Power Supply 7 Strobe Light

3 Vibration Sensors 8 Inductive Pickup

4 Software Cartridge 9 Holding Strap

5 Magnet

Figure 10 EVA

The EVA allows for a systematic collection of information that is necessary to accurately

diagnose and repair NVH problems. The tool uses an electronic pick-up that measures vibration

frequency and amplitude. An additional pick-up can be added and two sources of vibrations can

be compared. The pick-ups can be placed anywhere on the vehicle. By placing the pick-up on

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the source of the vibration can be located by the highest amplitude. If the steering wheel or

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The EVA can record snapshots during a road test and the data replayed to determine the vibration

frequency. This is useful for intermittent or short duration vibrations.

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frequency. The operation manual for the tool describes how to use this feature to help in

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propeller shafts.

22 Noise, Vibration, and Harshness

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MTS 4100

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1 Photo Tachometer 7 AC/DC Adapter

2 Microphone 8 DC Power Cable

3 Microphone 9 RS 232 Cable

4 Accelerometer 10 MTS 4100

5 Accelerometer 11 Timing Light

6 OBDII Cable

Figure 11 MTS 4100

The MTS 4100 NVH Analyzer can help identify, isolate, and repair NVH concerns.

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engine and transmission controllers to match the vibrations or noises with their possible

sources.

=� It also includes a propeller shaft balancing function to assist in the repair phase of these

vehicles.

=� You can also use the MTS 4100 to record and replay test results both before and after

diagnostic procedures.

Noise, Vibration, and Harshness 23

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ROAD TESTING FOR RESULTS

To properly diagnose and repair NVH concerns, the concern will need to be duplicated during a

road test. The symptoms and facts surrounding the concern should be documented on the NVH

Diagnostic Worksheet. Proper questioning of the customer by service writer/advisor will usually

provide the information necessary to duplicate the concern.

Determine which test equipment is needed for the road test. If utilizing test equipment during a

road test, it is a best practice to have an assistant drive while the equipment is being monitored

and the results recorded on the NVH Diagnostic Worksheet.

WARNING: DURING A ROAD TEST, AN ASSISTANT SHOULD DRIVE WHILE THE EQUIPMENT IS BEING MONITORED AND THE RESULTS RECORDED ON THE NVH DIAGNOSTIC WORKSHEET.

WARNING: DO NOT SHUT THE ENGINE OFF DURING A ROAD TEST. THIS WILL CAUSE LOSS OF STEERING CONTROL AND BRAKING.

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vibration occur. The steps of the slow acceleration test are:

1. Slowly accelerate the vehicle to the speed in which the problem occurs.

2. Note the vehicle speed and the engine rpm.

3. If possible, determine the frequency of the noise or vibration.

4. Record all results on the NVH Diagnostic Worksheet.

5. Classify the noise or vibration.

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The neutral coast down speed test divides the possible causes of the noise or vibration into two

categories:

=� Vehicle-speed-related

=� Engine-speed-related

The steps of the neutral coast down speed test are:

1. Drive the vehicle at a speed higher than the speed in which the noise or vibration was

obvious in the slow acceleration test.

2. Place the vehicle in neutral and coast down through the speed where the concern occurs.

3. Classify the NVH concern as either vehicle-speed-related or engine-speed-related.

=� If the noise or vibration exists, then the concern is vehicle-speed-related. This eliminates

the engine and torque converter as possible causes.

=� If the NVH concern did not occur during the neutral coast down speed test, perform a

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24 Noise, Vibration, and Harshness

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The NVH Diagnostic Worksheet contains the formulas required to calculate the frequencies for the

following component groups:

=� Wheel and tire

=� Driveline

=� Engine

=� Engine accessory

The NVH Diagnostic Worksheet will perform all the necessary calculations.

The formula and the steps required to calculate wheel and tire frequency manually is listed below.

8 km/h (5 mph) increments = vehicle speed/5

You can calculate wheel and tire frequency manually by performing the following steps:

1. Divide the vehicle speed by 5.

=� The resulting number indicates the number of 8 km/h (5 mph) increments

2. Obtain the corresponding tire size frequency at 8 km/h (5 mph).

=� This information is in a standard tire revolution chart located in the Appendix

3. Multiply the 8 km/h (5 mph) increment by the revolutions per second at 8 km/h (5 mph).

=� Wheel and tire frequency = tire size frequency x number of 8 km/h (5 mph) increments

Noise, Vibration, and Harshness 25

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The following items should be recorded during the road test and the results should be entered in

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=� Tire size

=� Frequency measured

=� Engine speed

=� The speed at which the vibration occurs

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>��Z&��%?��>��$��*�:�������$���:��������%��?���������������'�%���%�%�/'������+��&'K

The NVH Diagnostic Worksheet has a threshold of +/– 2 Hz.

For example, the if the measured frequency is 14 Hz and the wheel and tire frequency is 11 Hz the

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number of disturbances created in one complete revolution or cycle of a component. The second-

order frequency of the wheel and tire component group is twice this number. The third-order

frequency is three times this number.

If the frequency measured is 12 Hz, and the wheel and tire frequency is also 12 Hz, this directly

relates the vibration to the wheel and tire component group.

26 Noise, Vibration, and Harshness

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2034-91_011

Figure 12 Wheel and Tire Balance

A wheel and tire that is out of balance will cause a vibration.

=� $���������/�+������$�����&���������:���@���'���������$����%�������>��$��@��+$�������$��@$����

and tire as it rotates

=� The second image represents how an imbalance will cause the wheel to wobble, which

can cause ride disturbances, usually vertical and lateral vibrations; it can also result in a

wobbling of the steering wheel

=� The third image demonstrates how ride disturbance usually increases with speed

Wheel and tire related vibrations are also caused by:

=� A wheel or tire that is out of round

=� �������>��%��*����������[���>>��'��������$������{������@���\�

=� Drive axle problems

=� Condition of the wheels and tires

=� Brake rotor or brake drum imbalance

=� Excessive hub runout

Noise, Vibration, and Harshness 27

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2034-91_012

Figure 13 Radial Force

Radial force variation is a term describing the tire uniformity under load, measuring the variation

of the load acting on the vehicle spindle. Tires provide traction for steering, acceleration, braking,

and load support by transmitting forces between the vehicle and the road. High values of radial

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that will drive disturbances into the vehicle in the vertical direction.

To understand the effects of radial force variation on vibration, a model of a tire can be used. The

sidewall and footprint can be understood as a collection of springs between the wheel and the tire

contact patch. If the sidewall stiffness is not uniform, a vertical force is exerted on the axle and

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the vehicle unrelated to balance.

Note: A tire with noticeable radial force variation will produce a vibration even though it is perfectly balanced and is within the radial and lateral runout limits.

As the wheel and tire rotates under load, a lack of uniformity in the sidewall of the tire may cause

the wheel to wobble, which can cause ride disturbances, usually vertical and lateral vibrations. It

can also result in a wobbling of the steering wheel.

28 Noise, Vibration, and Harshness

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2034-91_013

Figure 14 Radial Force Variation

All tires have some non-uniformity in the sidewall and/or footprint due to variables in the

manufacturing process. Tire uniformity measurement values can be affected by the width and

condition of the wheel as well as many diverse tire-mounting variables. Unlike balancing, there is

often a small amount of radial force variation remaining in the wheel and tire assembly after match

mounting.

Radial force variation can be measured by a load roller pressing against a rotating tire and wheel

assembly to evaluate the magnitude of existing assembly harmonics. The Hunter GSP 9700

Series Vibration Control System is one means of determining and possibly correcting radial force

variation.

Noise, Vibration, and Harshness 29

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MEASURING WHEEL AND TIRE RUNOUT

Excessive wheel and tire runout can cause a noticeable vibration. As the vehicle is driven, the

wheels and tires are exposed to great stresses and abuse. Wheels can bend and tires can separate,

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in the chart below.

Table 1 Typical Wheel and Tire Runout Limits

Radial RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.25 mm (0.010 in.)

Steel Wheels 0.51 mm (0.020 in.)

Lateral RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.76 mm (0.030 in.)

Steel Wheels 0.76 mm (0.030 in.)

Note: Prior to performing a runout measurement, you must ensure that the tire beads are seated equally around the circumference of the tire.

30 Noise, Vibration, and Harshness

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2034-91_014

Figure 15 System Radial Runout

This on-the-vehicle system check will measure the radial runout of the hub, wheel, and tire.

=� ������*�$�%������������%����������

=� Prepare the tire by wiping off the tread

=� Apply masking tape around the circumference of the tire in the locations to be measured

(do not overlap the tape)

=� Check system runout using a dial indicator with wheel or wide tip

=� Place the end of the indicator against each taped area (one at a time) and rotate the tire and

wheel; system radial runout should not exceed 0.76 mm (0.030 in.) with no tread dips or

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Noise, Vibration, and Harshness 31

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21

3

2034-91_015

1 Tire Location Mark 3 Valve Stem

2 High Spot

Figure 16 Radial Runout

This radial runout check is performed with the tire and wheel assembly off the vehicle, to measure

the radial runout follow the steps below:

=� Remove tire and wheel assembly from vehicle and install it on a suitable wheel balancer

=� Prepare the tire by wiping off the tread

=� Apply masking tape around the circumference of the tire in the locations to be measured

(do not overlap the tape)

=� Place the end of the indicator against each taped area (one at a time) and rotate the tire and

wheel

– Radial runout should not exceed 0.76 mm (0.030 in.) with no tread dips or steps

– �������'���������'��%���:�������������:?��'�Q����>��$�����������%�����+�&+�

=� If the runout exceeds the limits, mark the original location of the tire on the wheel at the

valve stem (positions 1 and 3)

– Mark the tire and wheel to indicate the original high spot (position 2) of the assembly

and record the runout measurement

=� If the runout exceeds the limits, the tire will need to be dismounted from the wheel to verify

wheel versus tire contribution (refer to wheel runout measurement)

32 Noise, Vibration, and Harshness

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2034-91_041

Figure 17 Lateral Tire Runout

Lateral runout for the vehicle system as well as the tire and wheel assembly should be less than

0.76 mm (0.030 in). The same procedure and theory described for radial runout can also be

applied to identify and reduce lateral runout.

Noise, Vibration, and Harshness 33

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2034-91_016

Figure 18 Wheel Runout

=� Dismount the tire from the wheel

=� Mount the wheel back on the wheel balancer

=� Measure radial runout of the wheel at the tire bead seat

– �&��&���$�&���������%�����$���'�%���%��������/��������������$����:��

– Replace the wheel if it exceeds the limit

Table 2 Typical Wheel and Tire Runout Limits

Radial RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.25 mm (0.010 in.)

Steel Wheels 0.51 mm (0.020 in.)

Lateral RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.76 mm (0.030 in.)

Steel Wheels 0.76 mm (0.030 in.)

34 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 35

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LESSON 3 � $.-�' -.�& �(3 -(6$-�(-. -(6'�((�� /&$ �-'

�& �(3 -(6'�((�6&(3$(�� /&$ �-'

The process to diagnose and repair NVH concerns is consistent regardless of the component group

involved.

In this lesson we will focus on the following component groups:

=� Driveline

=� Engine

=� Engine accessory

Noise and vibration that occur during driving have various sources. During the initial vehicle road

test, different road test procedures are used to relate the symptoms into two groups. The two

groups are:

=� Engine-speed-related

=� Vehicle-speed-related

Using the frequency of the vibration and mathematical formulas, the cause of the noise or

vibration can be isolated into the following component groups:

=� Driveline

=� Wheel and tire

=� Engine

=� Engine accessory

36 Noise, Vibration, and Harshness

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&��������

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component group. Depending on the concern, different road test procedures can be used to load

or unload the engine, torque converter, suspension, driveline, and wheel bearings. Depending on

the concern, certain checks may or may not be necessary.

Different road test procedures are used determine the conditions under which a noise or vibration

occurs. The following items should be monitored and recorded on the NVH diagnostic sheet.

=� Engine speed

=� Vehicle speed

=� Frequency of the noise or vibration

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Slowly accelerate the vehicle to identify the speed at which a noise or vibration occurs. Continue

by using the neutral coast down to divide the possible causes of the noise or vibration into two

categories.

=� Vehicle-speed-related

=� Engine-speed-related

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can be used to relate the possible cause to the driveline or wheel and tire component group.

Noise, Vibration, and Harshness 37

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2034-91-017

Figure 19 Driveline Vibrations

Driveline-related concerns are usually caused by the following conditions:

=� A propeller shaft imbalance

=� A damaged propeller shaft

=� Improper propeller shaft operating angles

=� Worn universal joint

=� Worn center bearings

=� Loose spring U-bolts

=� Loose or broken springs

=� Damaged axle shaft bearings

=� Loose pinion gear nut

=� ��%����*��'����������+���&��&�

38 Noise, Vibration, and Harshness

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2034-91_018

Figure 20 Propeller Shafts

The function of a propeller shaft is to transmit power from one point to another in a smooth

action. The shaft is designed to send torque through an angle from the transmission (transfer case

on 4WD vehicles) to the axle.

Propeller shafts are balanced by the manufacturer with weights spot-welded to the tube. The shaft

is designed and built with the yoke lugs in line with each other, which is called phasing. When two

shafts come together at a common joint, the angle that is formed is called the operating angle.

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second-order vibration may be caused by propeller shaft angle, universal joint cancellation, and

worn universal joints.

Caution: Use exact replacement parts for attaching the propeller shafts. This ensures �����������������������!�"��#����$%��&%����'*�+��-�����'��#�*������0������0�the fasteners.

Noise, Vibration, and Harshness 39

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1 2 32034-91_019

1 Front Measurement 3 Rear Measurement

2 Center Measurement

Figure 21 Propeller Shaft Runout

If a bent propeller shaft is suspected, perform a runout check on the propeller shaft. The dial

indicator must be placed at a 90 degree angle from the propeller shaft for accurate readings. First,

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information. The second measurement is done in the center of the propeller shaft to verify it is

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replaced.

WARNING: WHEN WORKING AROUND MOVING PARTS, MAKE SURE THAT LONG SLEEVES ARE BUTTONED, NECKTIES ARE TUCKED INSIDE YOUR SHIRT, AND THAT LONG HAIR IS TIED BACK AND TUCKED UNDER A HAT

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Table 3 ?'�%������'������$�>���&��&��'�%���%������

Front Center Rear50 mm (0.020 in.) 63 mm (0.025 in.) 50 mm (0.020 in.)

40 Noise, Vibration, and Harshness

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The frequency range of a propeller shaft is usually 3 to 4 times the frequency of a component in

the wheel and tire component group. CV shafts and half shafts revolve at the same frequency as

the wheels and tires, which is usually in the range of 10–15 Hz at highway speeds. The frequency

of a propeller shaft vibration is usually in the range of 30–60 Hz at highway speeds.

Knowing the wheel and tire frequency allows for easy calculation of propeller shaft frequency.

The propeller shaft drives the tires through the rear axle. Therefore, to determine propeller shaft

frequency, multiply the wheel and tire frequency by the ratio of the rear axle.

The NVH diagnostic sheet will perform at the necessary calculations to determine the propeller

shaft frequency. Propeller shaft frequency can also be calculated manually by using the

mathematical formula below.

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Calculate propeller shaft frequency by performing the following steps:

1. Obtain the axle ratio (the axle ratio can always be found on the VIP report)

2. Multiply the wheel and tire frequency by the rear axle ratio

For example:

Using the following information, we can calculate the propeller shaft frequency

=� A vehicle has a vibration concern when driving 40 mph

=� The rear axle ratio is 4.0:1

=� The wheel and tire frequency is 10 Hz

Multiply the wheel and tire frequency (10 Hz) with rear axle the ratio (4.0), the result is a

calculated frequency of 40 Hz.

Propeller shaft concerns can be in one of the following areas:

=� Damaged propeller shafts

=� Missing weights

=� Transmission or transfer case output shafts

=� �����������+���&��&�

=� Pinion bearing or pinion gear problems

=� Worn universal joints

=� Loose pinion gear nut

=� Improper operating angles

=� Pitch line runout

Noise, Vibration, and Harshness

Diagnosing Driveline- and Engine-speed Vibra ons

1

2034-91 091

42 Noise, Vibration, and Harshness

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Driveline operating angle refers to the angle that is formed by the intersection of two shafts. The

procedure for measuring and correcting driveline operating angles depends on whether the

vehicle is equipped with a one- or two-piece propeller shaft.

Procedures for the one-piece systems should be understood before attempting to correct a

two-piece system. An inclinometer (Miller Tool # 7663) will be necessary to perform these

measurements.

The operating angle of a universal joint is the difference between the angles formed when two

shafts intersect. In a one-piece propeller shaft system, there are two operating angles present: the

front and the rear.

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Operating angles should not be equal to zero. With a zero operating angle, the needle bearings

within a universal joint will not rotate, causing brinelling and premature wear of the universal

joint.

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Noise, Vibration, and Harshness 43

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21

2034-91_020

1 Front Operating Angle 2 Rear Operating Angle

Figure 23 Propeller Shaft Operating Angles

The rear operating angle is formed by the angle of the propeller shaft and the angle of the rear axle

pinion. The front operating angle is formed by the angle of the propeller shaft and the angle of the

transmission output shaft.

The angles of these components are measured most accurately from the universal joint bearing

caps.

The bearing caps should be free of corrosion or foreign material for accurate readings. Remove

any snap rings that may interfere with the correct placement of the inclinometer and reinstall

them after the measurements have been taken.

44 Noise, Vibration, and Harshness

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23

45

1

2034-91_021

1 Angle C 4 Angle A

2 Input Yoke 5 Output Yoke

3 Angle B

Figure 24 Measuring Operating Angles

The following steps apply to both the front and rear propeller shafts. To obtain the front operating

angle on the front propeller shaft, position the inclinometer on the machined surface of the

universal joint.

Noise, Vibration, and Harshness 45

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2034-91_0022

Figure 25 Transmission Yoke Measurement

1. To check driveline alignment, raise and support the vehicle at the axles as level as possible.

Allow the wheels and propeller shaft to turn.

2. Remove any external bearing snap rings, if equipped, from the universal joint so the

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3. Rotate the shaft until the transmission/transfer case output yoke bearing is facing

downward.

4. Place the inclinometer on the yoke bearing parallel to the shaft. Center the bubble in the

sight glass and record the measurement. This measurement gives you the transmission

yoke output angle.

46 Noise, Vibration, and Harshness

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2034-91_0023

Figure 26 Propeller Shaft Measurement

5. Rotate the propeller shaft 90 degrees and place the inclinometer on the yoke bearing

parallel to the shaft. Center the bubble in the sight glass and record the measurement. This

measurement can also be taken at the rear of the shaft. This measurement gives you the

propeller shaft angle.

Noise, Vibration, and Harshness 47

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2034-91_0024

Figure 27 Pinion Flange Measurement

6. ��������$��'��'�������$�>���}���+���������'��%���$����%����/���������$��%�/'����������+��

yoke bearing parallel to the shaft. Center the bubble in the sight glass and record the

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7. &:���%���$���/��������+&���>��/��$�����+���[/���&��/������/��&��/���&��/�����\����

obtain the transmission/transfer case output operating angle.

8. &:���%���$���/��������+&���>��/��$�����+���[/���&��/������/��&��/���&��/�����\����

obtain the axle input operating angle.

Keep these things in mind for proper universal joint cancellation:

=� The front and rear angles need to be within one degree of each other

=� Operating angles should be less than 3 degrees

=� The rear angle has to bigger than the front

=� Must have at least 1/2 of one degree operating angle to keep the lubrication moving

through the universal joint

48 Noise, Vibration, and Harshness

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2034-91_0025

Figure 28 Engine-speed Vibration

Engine-speed-related vibrations are caused by a component that is driven by the engine. These

components may be part of the engine assembly or an engine accessory.

Using the frequency of the vibration and mathematical formulas, the noise or vibration can be

isolated into these component groups:

=� Engine

=� Engine accessory

Noise, Vibration, and Harshness 49

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2034-91-026

Figure 29 Engine Frequency Formula

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can be used to determine if the vibration is caused by the engine or accessory drive. The engine

frequency formula can be used to calculate engine frequency.

For purposes of vibration diagnosis, the engine component group also includes the torque

converter and exhaust system.

=� Divide the engine rpm by 60

=� First-order engine frequency = rpm/60

=� �%���^��������+����>��Z&��%?��������^������>��Z&��%?���|

=� $���^��������+����>��Z&��%?��������^������>��Z&��%?���~

50 Noise, Vibration, and Harshness

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First- and second-order engine noise and vibration is generated by the reciprocating motion of the

pistons and the rotating mass of other engine components.

Some of the causes of these normal noises and vibrations include:

=� Combustion

=� Friction

Noises and vibrations are generated by the impact between reciprocating components. As the

pistons reciprocate, the clearance between parts is repeatedly pulled in alternating directions.

Noise and vibration are created as the gap between the moving parts cycle between tension and

compression. First- and second-order engine vibrations are usually detected during the neutral

run-up test.

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First-order vibration is created when any component that rotates at crankshaft speed is out

�>�:����%�����$�����%����*���&��&�K�����/'����������?@$����������Z&��%��*�������/:����%������

cylinder-to-cylinder mass differences. In rare cases, the crankshaft itself may be imbalanced.

Balancing the component or correcting the runout may bring the vibration to an acceptable level.

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The torque converter frequency is the same as the engine frequency. The torque converter can

be suspected as the cause of noise or vibration when an NVH concern is torque sensitive. The

vibration may appear or disappear at different vehicle speeds, but may be present at the same

engine rpm.

For example, if a vehicle has a noise or vibration at 25 mph, 40 mph, and 65 mph, but is worse at

a particular speed, the NVH concern is probably torque sensitive because the condition occurs at

the same engine rpm but in a different gear. Use the torque converter test to determine how the

torque converter contributes to an engine-speed-related condition.

Noise, Vibration, and Harshness 51

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'�������������������

Second-order vibration is caused by the up-and-down motion of the pistons. This reversal of mass

and motion creates a natural vibration.

Symptoms of engine imbalance include:

=� A low-speed shake felt between 480 and 1,200 rpm that has a frequency of 8 to 20 Hz

=� A roughness sometimes felt and heard between 1,200 to 3,000 rpm at a frequency of 20 to

50 Hz

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A half-order engine vibration is created when any component that rotates at half the crankshaft

speed is out-of-balance or has excessive runout. An example of this is camshaft imbalance.

Balancing the component or correcting the runout may bring the vibration to an acceptable level.

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�>��$��%�/:&������%�����������'&���;�����@��$��$��%?�������������+���������;������&����*�:�������

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becomes. Vibrations also increase when the engine has a problem that interferes with the normal

combustion cycle.

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may increase with the accessories loaded. For example: if the engine mount is grounded, the

engine mount will create a transfer path for noise and vibration.

�>������!�%��%��������>>�%����:?������+�>��Z&��%?;����/�?�%�&����������%���������$���%�/'������

@$������'�%���%��'/�������%$��K�������+�>��Z&��%?�%��%�����&�&���?�$�*���������@��'/����+�K�� ��

'��*�����$��*�:��������%�������:?������+�'&�����>��/�:�%�/��+������!�%��%���;��$��*�:�������/&���

be isolated. Motor mounts are designed to minimize the amount of vibration that reaches the

passenger compartment.

?/'��/���>������+�>��Z&��%?���!�%��%�������%�&��_

=� Sensitivity to engine rpm

=� Sensitivity to torque

=� Sensitivity to engine load

=� Droning

52 Noise, Vibration, and Harshness

������������������������������������������ ���

��%�������!�����<(=��#��

2034-91_027

Figure 30 Compelling Force of Exhaust

The compelling force of exhaust exiting each cylinder creates a pulsation on the exhaust manifold.

The pulsating pressure at the exhaust manifold produces acoustic energy, which is transmitted

to the exhaust pipe. The pulsating sound waves traveling through the exhaust pipe are a source

�>�*�:�������>����$����$�&����?���/K����$�&���*�:��������%���:�%�/���/'�������:?����������+�@��$�

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combination of these vibrations produces unwanted NVH concerns.

The combination of engine and exhaust vibrations within the exhaust system must be isolated to

prevent them from acting on the body of the vehicle. Exhaust hangers are used to suspend the

exhaust pipe from the body and to prevent transmission of vibration to the body.

Noise, Vibration, and Harshness 53

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2034-91-028

Figure 31 Engine Accessory Vibration

Engine accessories are a source of engine vibration. For example, air conditioning compressors

are susceptible to overcharging, which can result in an NVH condition. With the advent of

serpentine belts, it is no longer possible to remove belts one at a time to isolate the source

component. Because the serpentine belt drives all components, one component may affect

another through resonance.

If removing the serpentine belt eliminates the vibration, reinstall the belt and operate each

component separately. By turning the air conditioning on and off, or by turning the steering wheel,

some components can be eliminated or isolated as NVH sources. When diagnosing accessory

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frequencies.

54 Noise, Vibration, and Harshness

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����#�����(�����$��������!��"#����

Engine accessories produce vibrations at different frequencies than the engine itself. This is

because the drive ratio created by the different sized pulleys causes them to rotate at different

speeds. Accessory pulley misalignment or faulty components can also cause vibrations.

Determining engine accessory frequency is comparable to calculating driveline frequency.

The NVH diagnostic sheet contains the formula and will perform the necessary calculations to

determine the engine accessory frequency. Engine accessory frequency can also be calculated

using the mathematical formula below.

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Calculate engine accessory frequency by performing the following steps:

=� Determine the pulley ratio between the accessory pulley and the crankshaft pulley

=� Multiply the engine rpm where the NVH condition occurs by the pulley ratio

– Accessory rpm = engine rpm x pulley ratio

=� Divide the accessory rpm by 60 (the number of seconds in a minute)

Noise, Vibration, and Harshness 55

Notes:

56 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 57

Diagnosing Noise

LESSON 4 DIAGNOSING NOISE

GENERATION OF NOISE

Whenever a vehicle is in motion, the driveline produces sounds that can be a normal part of

operation. A vehicle may also produce sounds that may indicate a repair may be required.

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abnormal condition. Some of the different types of noises are:

=� Road noise

=� ������+

=� ���@�

=� Whine

=� !�@�

Droning Noise

������+�%����%%&��@$����%%��������+;���%��������+;�������*��+������%���������'���;�:&��/�����>����

�%%&���@$����%%��������+K��������+�&�&���?�����''������������'�%���%���+�����'�������*�$�%����'���K��

�$��������������+���*�$�%���@��$���������+�%��%���;��$��������/�?��%%&��������'�%���%�*�$�%���

�'���;������+�����'/;�?�&��$�&���%$��+��*�$�%����'����*��?����@�?K���$��+��+�*�$�%����'����

Z&�%Q�?�/�Q��������>��%&������%$�%Q��$��������+�:�%�&�����+�����'����'�������$��&+$��$���'�%���%�

���+������Z&�%Q�?K

#�'��������������+�%����%%&��@$�����+�����������*������*�:�����������������/����������$��:��?�

�>��$��*�$�%���%�&���+���������������K������%������;���������Q�;�������$�&����������%���%�/:��������

%�&���������+�����$��'�����+���%�/'���/���K��

A drone noise can be caused by a transfer path created by:

=� ��������+��&������&����+����/�&���

=� ����/�+������+��&������&����$�&����?���/

A drone noise can also be caused by:

=� Imbalanced or bent propeller shaft

58 Noise, Vibration, and Harshness

Diagnosing Noise

Tire Noise

2034-91_029

��+&���~|��Tire Noise

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�>���@����������K��j�����&���/��&>�%�&������>>������^�������������������+������Z&�'/��������$����

vehicles.

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Noise, Vibration, and Harshness 59

Diagnosing Noise

��>�������-����

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���+$��%$�������&���+���@��'�����&���;�@$�%$�������$��+�/�����$����$��%�&�%$�������+��$������:K�����

������+�@��$��$����%��%����;��������/'����������&���������������/���%���������������'������������$��

customer in terms they can understand.

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=� !�@�

=� ���@�

=� Whine

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�$��������$�&��������;�@$�%$�%��������?�:��%��>&����@��$�+����@$���;�:&��%���:��$�����@$�����$��

*�$�%���������������?K�����/����%����;���$�@������$����+���>����&��&��%��%��������������+�%�/'������;�

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��>>���������������/�?�:������%��������>>������*�$�%��������+�����'����K������������������/�?������

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=� ��+$�����*��+

=� !��*?����*��+

=� Cruise

=� Coast

Note: It is important to understand that all gears make noise. Axle noises are inherent. When a noise is perceived as a concern, by the customer, it becomes an issue that requires further investigation.

�} Noise, Vibration, and Harshness

Diagnosing Noise

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2034-91_030

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Noise, Vibration, and Harshness 61

Diagnosing Noise

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2034-91-032

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=� ��%����*����>>����������&��&��

=� ��@�������+����'������+���

����$������/'����>���>>��������������������@$����+������K����@$����+����������&�&���?�*��?��������*��

������Z&����������;���������>�����%%�/'������:?���$�+$�'��%$������K����@$����+�������@�����>����:��

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Note: The whine sound may be caused by machining variation of the ring and pinion gear set. The whine sound may be caused by a ring and pinion gear set with a machine variance even though the gear backlash and contact pattern appear acceptable. In these rare cases, the technician will not be able to visually determine the machining variation and can only replace the gear set to address the whine condition.

�| Noise, Vibration, and Harshness

Diagnosing Noise

&��������

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different drive modes include:

=� ��+$�����*�;�@$�%$���������+$�;������?��%%�����������$��&+$��$�����+����'���

=� �����;�@$�����$�����+����'�������/��������������$��+��������������&����������$�����*������

=� !��*?����*�;�@$�%$������'����%%�����������$��&+$��$�����+����'����@��$�&�����&%��+���

��@��$�>�

=� �����������%�����������$��&+$��$�����+����'����

=� ��&���;�@$�%$���*��*���/���������+����+����'����@��$�&���%%��������+������%��������+

=� &���;�'��>��/��+���>��������+$���&�������������&����������$�>��:�����+�

�:���������*��j���������'�������+��

Road-test Drive Modes Road-test Speed Ranges��+$�����*� �}����Q/J$�[|��~��/'$\

Float ����|�Q/J$�[~�����/'$\

Heavy drive �|����Q/J$�[������/'$\

Coast ���]}��Q/J$�[������/'$\

Cruise ]}��Q/J$�[���/'$\������:�*�

Noise, Vibration, and Harshness� �~

Diagnosing Noise

�����������

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produced by a component in a different area of the vehicle.

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�$��*�$�%��K�� $��������%�&����:?��$������%�����������+��'$����$��&+$��$��>&�������;�:&�������&��������

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�� Noise, Vibration, and Harshness

Diagnosing Noise

?��������������($&

2034-91_033

��+&���~���ChassisEAR

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'��%��+�%��/'���������%�����������>���*�$�%���������������+�����/'���������&�����$��&+$��������>�

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clamps in different locations at the same time to identify the source of the noise.

WARNING: DO NOT WEAR HEADPHONES WHILE OPERATING THE VEHICLE. USE A SECOND PERSON TO DRIVE THE CAR. IT IS AGAINST MANY STATE MOTOR VEHICLE LAWS TO OPERATE A VEHICLE WHILE WEARING HEADPHONES.

Caution: When removing jacks from the control box, do not pull on the microphone clamp wires. Damage to equipment may result.

Caution: Ensure the microphone leads are not against the exhaust pipe or any other location that could cause damage.

Noise, Vibration, and Harshness 65

Diagnosing Noise

$@���������'������

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%�/'������K���&���+������������;�/��?�%�/'��������������/�Q���$����/������������@$����$��

*�$�%�����������$����K�� ���%%&�����?����+��������&����^*�$�%���'��:��/;��'�������$��*�$�%�������$��

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Some of these components include:

=� �$����:�����+�

=� ���Q��%���'���

=� ���������

=� ���>�����%�����'���+�

=� Differential

=� Transmission

=� �&�������%����

=� Generator

=� Water pump

=� ��@����������+�'&/'

=� �J��%�/'�������

66 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 67

Harshness

LESSON 5 HARSHNESS

HARSHNESS

Suspension Components

2034-91-034

Figure 36 Suspension Components

Harshness has become a universal term when dealing with NVH concerns on a vehicle. Harshness

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associated with an abrupt thumping noise while driving over road joints or variations in road

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68 Noise, Vibration, and Harshness

Harshness

Struts and Shocks

Harshness concerns may be due to a component that is not allowed to move within its normal

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A worn strut or shock can cause excessive suspension travel, this can also cause low jounce

bumper clearance. This can result with sprung and unsprung mass coming in contact with each

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properly installed to avoid NVH concerns in the suspension.

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Noise, Vibration, and Harshness 69

Harshness

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2034-91-035

Figure 37 Tire Placard

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rigid tires do not absorb harshness as well.

70 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 71

GLOSSARYamplitude The vertical measurement between the top and bottom of a wave

audible range of sound Sound that is in the range of 20 to 20,000 Hz

beat An NVH concern produced by two sounds that is most noticeable

when the frequency difference is 1 to 6 Hz

brake shudder Vibration that causes the instrument panel, steering wheel, and

sometimes the entire body to vibrate vertically and back-and-forth

during braking; it also may result in brake pedal pulsation related to

wheel rotation

brake squeal A high pitched brake noise that can be short in duration if it is due to

dampness

ChassisEAR A versatile electronic listening tool that allows the user to listen to

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compelling force An exciting force acting upon an object that causes it to vibrate

cycle The path a wave travels before the wave begins to repeat the path

again

downshift speed test $��*�$�%���%$�%Q��$���$��'�����%�����/��$����!�%��%���������+���^

speed-related

StarSCAN Chrysler’s latest generation, hand-held diagnostic scan tool

droning, high-speed A long duration, non-directional humming noise that is uncomfortable

to the ears and has a range of 80.5 km/h (50 mph) and up

droning, low-speed A long duration, low-pitched noise that is non-directional and has a

range of up to 48 km/h (30 mph)

droning, middle-speed A long duration, low-pitched noise that is non-directional and has a

range of 48–80.5 km/h (30–50 mph)

electronic vibration

analyzer (EVA)

An NVH diagnostic tool that measures frequency and amplitude

engine accessory test The vehicle check that helps locate faulty belts and accessories that

are causing engine speed-related NVH concerns

engine loaded test The vehicle check that helps to reproduce engine speed-related

concerns not evident with the neutral run up or neutral coast down

speed tests; it also identifies noise and vibration sensitive to engine

load or torque

frequency The number of complete cycles that occurs in a given period of time

harshness An aggressive suspension feel or lack of “give” in response to a single

input

intensity The physical quality of sound that relates to the amount and direction

of the flow of acoustic energy at a given speed

72 Noise, Vibration, and Harshness

medium Provides a path for sound waves to travel through

neutral coast down

speed test

The second vehicle check performed during a road test used to divide

the possible cause of a noise or vibration as vehicle-speed- or engine-

speed-related

neutral run-up test The vehicle check that is used as a follow-up to the downshift speed

test or when the NVH concern occurs at idle

noise Unpleasant or unexpected sound created by a vibrating object

NVH Diagnostic

Worksheet

A form used throughout the troubleshooting process to help verify,

analyze, and correct an NVH condition

order The number of disturbances created in one revolution of a component

pitch The physical quality of sound that relates to the frequency of the wave

radial tires Tires with high-belt rigidity that provide excellent steering and

stability and low-rolling resistance

resonance The tendency of a system to respond increasingly to a compelling

force oscillating at, or near, the natural frequency of the system

ride comfort A measurement of how well a vehicle suppresses abnormal vibrations;

poor ride comfort results when sprung or unsprung components

become worn or damaged

road noise Noise that occurs while driving on gravel or roughly paved roads at all

vehicle speeds, or when a vehicle is coasting

shake, lateral Side-to-side vibration of the body, seats, and steering wheel

shake, vertical Several vertical vibrations of the body, seats, and steering wheel

shimmy, high-speed Vibration that causes the steering wheel to oscillate when driving on

smooth roads at high speeds

shimmy, low-speed Vibration that causes the steering wheel to oscillate when driving

across a bump at low speeds

Six-step Diagnostic

Process

A systematic approach that incorporates the Six-step Diagnostic

Process to account for the multiple possibilities that may cause a noise

or vibration

slow acceleration test $��������*�$�%���%$�%Q�'��>��/����&���+�������������&�������������>?�

the noise or vibration

sound The result of a vibrating disturbance of an object producing waves that

transmits out from the source

Noise, Vibration, and Harshness 73

sprung components Components of a vehicle that are suspended by a spring such as the

body and suspension system

steering input test 1 The vehicle check that determines how wheel bearings and other

suspension components contribute to a vehicle-speed-related

condition

steering input test 2 The vehicle check that is performed if the NVH condition occurs only

when turning

unsprung components Components of a vehicle that are not suspended by a spring such as

the tires, axles, and wheels

vibration The repetitive motion of an object, back and forth or up and down

74 Noise, Vibration, and Harshness

Notes:

Noise, Vibration, and Harshness 75

APPENDIX

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Begin checking the vehicle with a visual inspection. Be sure to carefully inspect

the tires and wheel assemblies, unless the NVH concern only occurs at a standstill.

Before the road test, inspect the following:

Check the tires for:

=� ��������������'����&��

=� Proper tire type, verify the tires are uniform in size and brand

=� Properly installed tires and if the tire bead is uniform around the wheel

=� �:���/��������@���;��&%$����%&''��+;�������'���;��$�&�����@���;�>���$����+;�����%����%��������

groove depth

Check the wheels for:

=� Foreign debris, such as mud or ice in the wheels

=� Deformed or bent wheels

=� Missing wheel weights

=� �&+��&������Z&�������'�%���%�����

Check the vehicle for:

=� Obvious signs of damaged components

=� Indications of collision damage

=� Aftermarket components

76 Noise, Vibration, and Harshness

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Observe the following guidelines when preparing for the road test:

=� Check the customer repair order before beginning the road test

– �������/'����������Q��@�@$�%$��'�%���%�%��%�����$��%&���/���$���@��$��$��*�$�%��

– This prevents correcting the wrong concern and increasing the cost of the repair

=� Don’t be misled by the reported location of the noise or vibration

– The cause may actually be some distance away

=� Remember that the vibrating body may generate a small vibration only

– This small vibration in turn may cause a larger vibration or noise due to the vibrating

body’s contact with other components

=� Conduct the road test on a quiet street where safely duplicating the noise or vibration is

possible

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– It must be possible to operate the vehicle at the speed in which the condition occurs

=� Turn the radio, A/C, and heater blower off unless the concern only occurs when the radio,

A/C, or heater is on

=� Determine which test equipment, if any, is needed for the road test

=� For cold weather climates, snow and ice can be the cause of noise complaints

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The following checks help determine the engine-speed, vehicle speed, and frequency of the NVH

concern. Each helps eliminate possible components. Depending on the concern, certain checks

may or may not be necessary.

=� Slow acceleration test

=� Neutral coast down speed test

=� Downshift speed test

=� Torque converter test

=� Steering input test 1

=� Steering input test 2

=� Neutral run-up test

=� Engine loaded test

=� Engine accessory test

Noise, Vibration, and Harshness 77

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test is used to identify the noise or vibration if a road test with the customer is not possible. The

steps of the slow acceleration test are:

=� Slowly accelerate the vehicle to the speed in which the problem occurs

=� Note the vehicle speed and the engine rpm

=� If possible, determine the frequency of the noise or vibration

=� Classify the noise or vibration

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The neutral coast down speed test divides the possible causes of the noise or vibration into two

categories:

=� Vehicle-speed-related

=� Engine-speed-related

The steps of the neutral coast down speed test are:

1. Drive the vehicle at a speed higher than the speed in which the noise or vibration was

obvious in the slow acceleration test.

2. Place the vehicle in neutral and coast down through the speed where the concern occurs.

3. Classify the NVH concern as either vehicle-speed-related or engine-speed-related.

=� If the noise or vibration exists, then the concern is vehicle-speed-related. This eliminates

the engine and torque converter as possible causes.

=� If the NVH concern did not occur during the neutral coast down speed test, perform a

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1. Stop the vehicle and place the transmission in a lower gear.

2. Drive the vehicle at the engine rpm in which the noise or vibration occurs.

=� If the noise or vibration exists, then the concern is engine-speed-related (this eliminates

tires, wheels, brakes, and suspension components)

=� �>���%�����?;���'�����$�������&���+���$���+�����������&��������%�����/��$�����&���

78 Noise, Vibration, and Harshness

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The torque converter test determines how the torque converter contributes to an engine-speed-

related condition. The steps of the torque converter test are:

1. Drive the vehicle at the speed in which the NVH concern exists.

2. Operate the torque converter by taking it in and out of lock-up by lightly depressing the

brake pedal, while maintaining vehicle speed.

3. Check for noise when the torque converter is not locked up.

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The steering input test 1 determines how wheel bearings and other suspension components

contribute to a vehicle-speed-related condition. The steps of the steering input test 1 are:

1. Drive the vehicle at the speed in which the NVH concern exists.

2. Make wide sweeping turns in both directions.

=� If the concern goes away or gets worse, wheel bearings, hubs, universal joints, and tire

tread wear may be the cause of the concern

=� If the noise or vibration exists, then the concern is engine-speed-related (this eliminates

tires, wheels, brakes, driveline, and suspension components as the cause)

'������� ��#�����

Perform the steering input test 2 if the NVH condition occurs only when turning. The steps of

steering input test 2 are:

1. Drive the vehicle at a speed higher than the speed in which the noise or vibration occurs.

2. Place the vehicle in neutral and coast down through the speed where the NVH concern is

obvious, while making wide sweeping turns in both directions.

=� If the concern exists, check for worn wheel bearings, suspension bushings, and universal

joints (contained in the axles of 4WD applications)

=� If the vibration does not occur, stop the vehicle and engage the transmission or transaxle;

alternately accelerate and decelerate through the speed where the NVH concern appears,

while making wide sweeping turns in both directions

=� If the concern returns, then the cause is dependent upon engine load; the probable causes

are constant velocity (CV) boots, CV joints, universal joints (contained in the axles of 4WD

applications) and loose or missing lug nuts

=� If the noise is a clunking sound, engine and transaxle mounts, suspension bushings, and

universal joints are probable causes

Noise, Vibration, and Harshness 79

-�#����&#��#����

Perform the neutral run-up test if the NVH concern is engine-speed-related. Use the neutral run-

up test as a follow-up to the downshift test or when the NVH concern occurs at idle. The steps of

the neutral run-up test are:

1. Increase the engine rpm while in park on front-wheel drive vehicles or neutral on rear-

wheel drive vehicles.

2. If necessary, make note of the rpm and frequency of the NVH concern.

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Perform the engine loaded test if the NVH concern is engine-speed-related. This test may help

reproduce engine-speed-related concerns not evident with the neutral run-up or neutral coast

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torque. These NVH concerns often appear during heavy acceleration or when climbing a hill.

WARNING: BLOCK THE FRONT AND BACK WHEELS OR INJURY TO PERSONNEL MAY RESULT. DO NOT PERFORM THE ENGINE LOADED TEST FOR MORE THAN FIVE SECONDS OR DAMAGE TO THE TRANSMISSION/TRANSAXLE MAY RESULT.

The steps of the engine loaded test are:

1. Block the front and back wheels.

2. Apply the parking and service brakes.

3. Put the transmission in drive while keeping the brakes applied.

4. Increase the engine speed to the rpm in which the NVH concern occurred (if necessary,

make note of the rpm and frequency of the NVH concern).

5. Put the transmission in reverse while keeping the brakes applied.

6. Increase the engine speed to the rpm in which the NVH concern occurred (if necessary,

make note of the rpm and frequency of the NVH concern).

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narrow down the possible sources of the concern

80 Noise, Vibration, and Harshness

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Perform the engine accessory test if the NVH concern is engine-speed-related. This test helps

locate faulty belts and accessories that are causing engine-speed-related NVH concerns.

The steps of the engine accessory test are:

1. Block the front and back wheels.

2. Apply the parking and service brakes.

3. Remove the accessory drive belt(s).

4. Increase engine speed to the rpm in which the NVH concern occurred.

=� If the vibration occurs, the belts and accessories are not the source of the concern

=� If the belts and accessories are the source of the NVH concern, continue to add or remove

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Caution: Do not run the engine accessory test for more than a few minutes or the engine may overheat.

Noise, Vibration, and Harshness 81

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43

567

21

2034-91_036

Figure 38 Front-Wheel Drive NVH Concerns

1. Vibration and Noise: Engine Mounts, Accessories, Air Cleaner, Transaxle Belts, Binding,

Looseness, Misalignment, Wear, or Damage

2. Noise and Harshness: Suspension Wear, Misalignment, or Binding

3. Noise and Harshness: Suspension Wear, Misalignment, or Binding

4. High-speed Shake and Harshness: Wheel and Tire Runout, Imbalance, Non-uniformity,

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5. Noise and Vibration: Rear Wheel Bearing Roughness, Misadjustment, Drum Face, or Pilot

and Bolt Circle Runout

6. Moan and Boom: Exhaust System Binding, or Grounding

7. Noise and Vibration: Front Wheel Bearing Roughness, Rotor Flange, Pilot and Bolt Circle

Runout, or CV Joint Roughness

82 Noise, Vibration, and Harshness

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3 421

9 8 7 6 52034-91_037

Figure 39 Rear Wheel Drive NVH Concern

1. Moan, Accessory Vibration, and Harshness: Engine Mounts, Accessories, Air Cleaner, or

Belts

2. Boom and Vibration: Propeller Shaft Balance, Runout, Angle, or U-joint Binding

3. Driveline Vibration: Drive Axle Noise or Vibration

4. High Speed Shake and Harshness: Wheel and Tire Runout, Imbalance, Non-uniformity, or

���������

5. High Speed Shake and Axle Clunk: Brake Drum Imbalance, Axle Shaft End Play, Axle Flange

Face, or Pilot and Wheel Bolt Runout

6. Harshness: Rear Suspension Wear, Binding, or Misalignment

7. Moan and Boom: Exhaust System Binding, Grounding, or Misalignment

8. High Speed Shake and Noise: Brake Rotor Flange, Pilot and Wheel Bolt Runout, or Wheel

Bearing Roughness

9. Harshness and Noise: Suspension Wear, Damage, or Misalignments

Noise, Vibration, and Harshness 83

Table 5 Tire Revolution Chart

LIGHT TRUCK TIRES PASSENGER CAR TIRES PASSENGER CAR TIRESTire Size Revs/Sec.

at 8 km/h (5 mph)

Tire Size Revs/Sec. at

8 km/h (5 mph)

Tire Size Revs/Sec. at 8 km/h (5 mph)

LT215/75R15 1.04 P145/80R13 1.30 P215/65R17 1.03

LT245/70R15 1.02 P155/80R13 1.28 P215/70R15 1.08

LT215/75R16 1.01 P175/65R14 1.26 P215/75R17 1.04

LT215/85R16 0.95 P185/65R14 1.22 P220/75R15 1.03

LT225/60R16 1.08 P185/70R14 1.19 P225/45R17 1.16

LT225/75R16 0.98 P185/75R14 1.16 P225/55R17 1.08

LT225/75R17 0.95 P195/60R15 1.19 P225/60R16 1.09

LT245/70R16 0.98 P195/65R15 1.16 P225/60R18 1.01

LT245/75R16 0.94 P195/70R14 1.16 P225/65R17 1.01

LT265/70R17 0.91 P195/75R15 1.13 P225/65R16 1.04

LT295/40R20 0.99 P205/50R17 1.09 P225/70R15 1.06

30X9.5R15 0.98 P205/50R17XL 1.15 P225/75R15 1.02

31X10.5R16 0.95 P205/55R16 1.16 P225/70R16 1.02

P205/60R14 1.21 P225/75R16 0.99

P205/60R15 1.17 P225/70R15 1.04

P205/65R15 1.14 P235/75R15 1.00

P205/70R14 1.14 P235/35R17 1.10

P205/75R14 1.11 P235/55R19 0.99

P205/70R15 1.10 P235/75R16 0.97

P205/75R15 1.07 P245/75R16 0.95

P215/50R17 1.14 P245/65R17 0.98

P215/55R18 1.05 P245/45ZR20 1.01

P215/55R16 1.14 P245/50R20 0.97

P215/65R15 1.11 P275/40R17 1.13

P215/65R16 1.07

84 Noise, Vibration, and Harshness

(-. -(6'�((�6&(3$(�!&(Z?(-� ('

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Many NVH concerns are related to the engine systems. The operation of the engine creates a

natural vibration. If any one component is slightly out of balance, the natural vibration of the

engine is compounded. Engine vibration is generally caused by any of the following:

=� First- and second-order engine imbalance

=� ��+���������+�>��Z&��%?

=� Engine mounts

=� Engine accessories

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Use the engine rpm where the NVH symptom occurs to determine engine frequency. Calculate

engine frequency by performing the following step:

=� Divide the engine rpm by 60 (the number of seconds in a minute)

– Engine frequency = rpm/60

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engine is twice this number. Engine vibrations may also have half-order frequencies.

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Belt-driven engine accessories often produce vibrations at different frequencies than the engine

itself. This is because the drive ratio created by the different size pulleys causes them to rotate at

different speeds. Determining engine accessory frequency is comparable to calculating driveline

frequency. Calculate engine accessory frequency by performing the following steps:

1. Determine the size ratio between the accessory pulley and the crankshaft pulley.

=� Pulley ratio = crankshaft pulley diameter/accessory pulley diameter

2. Multiply the engine rpm where the NVH condition occurs by the number of times the

accessory pulley is rotating per crankshaft revolution.

=� Accessory rpm = engine rpm x pulley ratio

3. Divide the accessory rpm by 60 (the number of seconds in a minute).

=� Accessory frequency = accessory rpm/60

Noise, Vibration, and Harshness 85

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Noise and vibration that occur during driving have various sources. The major sources are the

following:

=� Rough or irregular road surfaces

=� Condition of the tires and wheels

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the close relationship that exists between the tire and road surface. Tires, just like the suspension,

body, and other components, are designed to minimize noise and vibration. The unique aspect of

tires is that they wear faster than other components. This is a contributing factor to wheel and

tire noise and vibration. Additionally, owners frequently replace original tires with different types.

This can result in tire and wheel imbalance, runout, or non-uniformity.

�����������.��#�

Use the vehicle speed in which the NVH symptom occurs to determine tire/wheel frequency.

Calculate tire/wheel frequency by performing the following steps:

1. Divide the vehicle speed by 5. The resulting number indicates the number of 8 km/h (5

mph) increments.

=� 8km/h (5 mph) increments = vehicle speed/5

2. Obtain the corresponding tire size frequency at 8 km/h (5 mph). This information is in a

standard tire revolution chart.

3. Multiply the 8 km/h (5 mph) increment by the revolutions per second at 8 km/h (5 mph).

=� Tire/Wheel frequency = tire size frequency x number of 8 km/h (5 mph) increments

$��%��%&������>��Z&��%?�����$�������^����������J@$����>��Z&��%?K����/�/:��;�����������$���&/:���

of disturbances created in one revolution of a component. The second-order frequency of the

wheel and tire assemblies is twice this number. The third-order frequency is three times this

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frequency, the cause of the problem can possibly be in the wheel and tire area.

86 Noise, Vibration, and Harshness

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Knowing the tire/wheel frequency allows for easy calculation of propeller shaft frequency. The

propeller shaft drives the tires through the rear axle. Therefore, to determine propeller shaft

frequency, multiply tire/wheel frequency by the ratio of the rear axle. Calculate propeller shaft

frequency by performing the following steps:

1. Obtain the axle ratio from the metal tag on the differential cover.

2. Multiply the tire/wheel frequency with the rear axle ratio.

=� Propeller shaft frequency = tire frequency x axle ratio

$��%��%&������>��Z&��%?�����$�������^������'��'�������$�>��>��Z&��%?K�� $����%���^������>��Z&��%?�

of the propeller shaft is twice this number.

It is important to remember the difference between propeller shaft and half shaft frequencies. The

frequency of propeller shaft concerns are high since they rotate approximately four times that of

the tire and wheel assemblies. Half shaft concerns are low frequency because they rotate at tire

and wheel speed.

Noise, Vibration, and Harshness 87

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2034-91_038

Figure 40 Propeller Shaft Balancing

There are two ways to balance a propeller shaft. There is one method in service information that

does not require any special tools. The propeller shaft also can be balanced using the EVA.

Note: Support the vehicle by the axle to maintain the driveline angle and prevent the wheels from contacting the ground while performing the procedure.

To set up the EVA to balance the propeller shaft, place the magnetic probe at the twelve o’clock

position on the rear axle input housing and connect it to the A input on the EVA. Connect the

strobe light to the inductive pickup trigger wire on the EVA and point it at the propeller shaft at

the six o’clock position. Also, connect the strobe light to the battery for power. Next, mark the

driveshaft at 90 degree intervals and number them from 1 to 4; place a shorter mark halfway

between each mark. The procedure to balance the propeller shaft is as follows:

1. Have another technician start the vehicle, put it in drive, and run the vehicle at the speed of

the vibration.

2. Hold the strobe light at the six o’clock position and determine where the propeller shaft is,

by using the marks on the shaft.

3. Stop the vehicle and place a hose clamp on the propeller shaft so the adjustment is at the

noted position.

4. Check for the vibration by having another technician repeat Step 1. If the vibration is

gone, add the correct amount of weight at the clamp location and remove the clamp. If the

vibration is still present, repeat the procedure and note the new location. The amount of

weight may be more or less than the weight of the clamp.

88 Noise, Vibration, and Harshness

��9�3((!�&9?3$'

(�������������!��%#��

=� Divide the engine rpm by 60 (the number of seconds in a minute)

=� Engine frequency = rpm/60

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=� $���^�������������^��������~

=� !��>^�������������^�����J|

(�����$��������!��%#��

=� Pulley ratio = crankshaft pulley diameter/accessory pulley diameter

=� Accessory rpm = engine rpm x pulley ratio

=� Accessory frequency = accessory rpm/60

(�����!�����!��"#����!��%#��

=� Divide the engine rpm in which the vibration occurs by 60

=� Multiply that number by the number of cylinders in the engine

=� j&���'�?��$����&/:���:?�}K��>����$����+���������+�>��Z&��%?

=� Hz = 0.5 [(engine-speed/60) x number of cylinders]

���������'��8!��"#����!��%#��

=� Propeller shaft frequency = tire/wheel frequency x axle ratio

Noise, Vibration, and Harshness 89

';�&!�&9?3$'

(�������������!��%#��

=� Engine frequency = rpm/60

(�����$��������!��%#��

=� Pulley ratio = crankshaft pulley diameter/accessory pulley diameter

=� Accessory frequency = engine frequency x pulley ratio

(�����!�����!��"#����!��%#��

=� Divide the engine rpm in which the vibration occurs by 60

=� Multiply that number by half the number of cylinders in the engine

=� ��+���������+�>��Z&��%?�����+����>��Z&��%?���$��>��&/:����>�%?�������

���������'��8!��"#����!��%#��

Propeller shaft frequency = tire/wheel frequency x axle ratio

90 Noise, Vibration, and Harshness

Notes:

NOISE, VIBRATION, AND HARSHNESS

ACTIVITY PACK0030708

Noise, Vibration, and Harshness

Causes of NVH Concerns

ACTIVITY 1 CAUSES OF NVH CONCERNS

2 Noise, Vibration, and Harshness

Causes of NVH Concerns

Notes:

Noise, Vibration, and Harshness 3

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ACTIVITY 2 �&(6&�$�(' -'�(� �-

For this activity, you will perform a pre-road test inspection on a vehicle.

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Table 1 Tire Checklist

Left Front Right Front Left Rear Right RearTire Size

Air PressureAbnormal Wear

Tread DepthVisible DamageWheel Weights

1. �$�%Q��$��*�$�%���>������������/�����+�:��?�'�����K���$�������?�&�����X

2. �$�%Q��$��*�$�%���>�����+����>�%�����������/�+�K���$�������?�&�����X

3. �$���'��:��/������?�&������@��$��$��*�$�%��X

4 Noise, Vibration, and Harshness

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Notes:

Noise, Vibration, and Harshness 5

Using the Sirometer

ACTIVITY 3 USING THE SIROMETER

The objective of this activity is to demonstrate the proper use of NVH diagnostic tools to analyze

the source of the concern.

Use the sirometer to determine the vibration frequency of the following items (If available).

WARNING: WEAR SAFETY GLASSES AND KEEP LOOSE OBJECTS AWAY FROM THE ROTATING OBJECTS.

1. What is the vibration frequency of a bench grinder?

2. What is the vibration frequency of a hand drill?

3. What is the vibration frequency of an idling engine?

4. What is the vibration frequency of a wheel balancer?

Pick two other items and measure the frequency for the two following questions.

5. What is the vibration frequency of _____________________________?

6. What is the vibration frequency of _____________________________?

6 Noise, Vibration, and Harshness

Using the Sirometer

Notes:

Noise, Vibration, and Harshness 7

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ACTIVITY 4 WHEEL AND TIRE VIBRATION DIAGNOSIS

The objective of this activity is to diagnose a wheel and tire vibration.

WARNING: BE SURE THAT ALL PEOPLE ARE CLEAR OF THE SPINNING WHEEL ASSEMBLIES.1. Place the vehicle on a hoist or on jack stands, so that the tires are off the ground.

2. Run the vehicle in drive so that the tires are spinning at a speed of 50–60 mph.

3. Using a Sirometer, EVA, or MTS 4100, measure the frequency of the vibration.

4. Complete the chart below, then enter the data on the NVH Diagnostic Worksheet.

Table 2 Diagnostic Worksheet Data

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Tire Size

Frequency

Vehicle Speed mph

Engine Speed rpm

Number of Engine Cylinders

Transmission Speeds

Axle Ratio

Engine Accessory Pulley Ratios P/S A/C Generator Water Pump

5. Input the data to the electronic version of the NVH Diagnostic Worksheet and use it to

calculate the frequencies.

6. Are there any frequencies that are close to the frequency that you measured? Which one(s)?

7. What is the most likely cause for the vibration?

8. How could you verify the cause of the concern?

8 Noise, Vibration, and Harshness

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Notes:

Noise, Vibration, and Harshness 9

Measuring Wheel and Tire Runout

ACTIVITY 5 MEASURING WHEEL AND TIRE RUNOUT

The objective of this activity is to measure the lateral and radial runout of both tires and wheels.

TASK 1 MEASURING RADIAL RUNOUT

2034-91_0101

Figure 1 Measuring Radial Runout

This on-the-vehicle system check will measure the radial runout including the hub, wheel, and tire.

1. ������*�$�%�������$��������%������$�������K��

2. Apply masking tape around the circumference of the tire in the locations to be measured. Do

not overlap the tape.

3. Check system runout using Dial Indicator Set, C-3339A with the 25-W wheel, or equivalent.

Set up the dial indicator as shown.

4. Place the end of the indicator against each taped area (one at a time) and rotate the tire and

wheel. System radial runout should not exceed 0.76 mm (0.030 in.) with no tread dips or

steps.

10 Noise, Vibration, and Harshness

Measuring Wheel and Tire Runout

5. �������'���������'��%���:�������������:?��'�Q����>��$�����������%�����+�&+�K

=� �������'���%���:�������������:?�����'�����%�������$�����%������������������%�����������+�

over 101.6 mm (4.0 in.) of tread circumference.

=� ��������'���%���:�������������:?�����'�����%�����������%������������������%�����������+��*���

101.6 mm (4.0 in.) of tread circumference.

6. What is the system radial runout?

Table 3 ��������&��&��'�%���%������

Radial RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.25 mm (0.010 in.)

Steel Wheels 0.51 mm (0.020 in.)

7. ��/'�����$����������&��&���+�������$���'�%���%������>��/��:�*�K���$�������?�&�����X

Noise, Vibration, and Harshness 11

Measuring Wheel and Tire Runout

TASK 2 MEASURING LATERAL RUNOUT

2034-91_0102

1. Set up the dial indicator as shown.

2. Be sure to place the roller tip on an area that is smooth all around the tire.

3. Rotate the wheel and note the reading on the dial indicator. What is the lateral runout on this

tire?

Table 4 ���������&��&��'�%���%������

Lateral RunoutTire 0.76 mm (0.030 in.)

Aluminum Wheels 0.76 mm (0.030 in.)

Steel Wheels 0.76 mm (0.030 in.)

4. ������$���@$������%�����$���'�%���%�����X

12 Noise, Vibration, and Harshness

Measuring Wheel and Tire Runout

Notes:

Noise, Vibration, and Harshness 13

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ACTIVITY 6 DRIVELINE VIBRATION DIAGNOSIS

The objective of this activity is to diagnose a driveline vibration.

WARNING: WEAR SAFETY GLASSES AND KEEP A SAFE DISTANCE FROM SPINNING WHEELS AND PROPELLER SHAFT ASSEMBLIES WHEN PERFORMING NVH DIAGNOSTIC TESTS.

1. With the vehicle on a hoist and the wheels off the ground, run the vehicle in drive at 35-50

mph.

2. Does the vehicle have a vibration?

3. Using a sirometer, EVA, or MTS 4100, measure the frequency of the vibration.

Table 5 Diagnostic Worksheet Data

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Tire Size

Frequency

Vehicle Speed mph

Engine Speed rpm

Number of Engine Cylinders

Transmission Speeds

Axle Ratio

Engine Accessory Pulley

Ratios

P/S A/C Generator Water Pump

4. Enter the required data on the NVH Diagnostic Worksheet to calculate the frequencies.

5. What was the frequency that you measured?

6. What is the most likely cause?

14 Noise, Vibration, and Harshness

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Notes:

Noise, Vibration, and Harshness 15

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ACTIVITY 7 ENGINE RELATED VIBRATION DIAGNOSIS I

The objective of this activity is to diagnose an engine speed related vibration.

WARNING: WEAR SAFETY GLASSES AND KEEP CLEAR OF ROTATING COMPONENTS WHEN PERFORMING NVH DIAGNOSTIC TESTS.

1. Perform the neutral run-up test.

2. Make note of the rpm that the vibration occurs at.

3. Using a sirometer and the EVA, measure the frequency of the vibration.

4. �����%���$����>��/������>��/��$��*�$�%����������������$��%$����:���@K

Table 6 Diagnostic Worksheet Data

��$�%�����������%�������&/:��

Tire Size

Frequency

Vehicle Speed mph

Engine Speed rpm

Number of Engine Cylinders

Transmission Speeds

Axle Ratio

Engine Accessory Pulley

Ratios

P/S A/C Generator Water Pump

5. Enter the required data on the NVH Diagnostic Worksheet to calculate the frequencies.

6. Are there any frequencies that are close to the frequency that you measured? Which one(s)?

7. What would be the most likely cause for the concern?

16 Noise, Vibration, and Harshness

�������"���������� �������������!

Notes:

Noise, Vibration, and Harshness 17

�������"���������� �������������!!

ACTIVITY 8 ENGINE RELATED VIBRATION DIAGNOSIS II

The objective of this activity is to diagnose an engine speed related vibration.

WARNING: WEAR SAFETY GLASSES AND KEEP CLEAR OF ROTATING COMPONENTS WHEN PERFORMING NVH DIAGNOSTIC TESTS.

1. Perform the neutral run-up test.

2. Make note of the rpm that the vibration occurs at.

3. Using a sirometer and the MTS 4100, measure the frequency of the vibration.

4. �����%���$����>��/������>��/��$��*�$�%����������������$��%$����:���@K

Table 7 Diagnostic Worksheet Data

��$�%�����������%�������&/:��

Tire Size

Frequency

Vehicle Speed mph

Engine Speed rpm

Number of Engine Cylinders

Transmission Speeds

Axle Ratio

Engine Accessory Pulley

Ratios

P/S A/C Generator Water Pump

5. Enter the required data on the NVH Diagnostic Worksheet to calculate the frequencies.

6. Are there any frequencies that are close to the frequency that you measured? Which one(s)?

7. What would be the most likely cause for the concern?

18 Noise, Vibration, and Harshness

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Notes:

Noise, Vibration, and Harshness 19

#�������������������$��%�&��������'������ ��

ACTIVITY 9 MEASURING PROPELLER SHAFT ANGLES DEMONSTRATION

WARNING: WEAR SAFETY GLASSES AND KEEP CLEAR OF ROTATING COMPONENTS WHEN PERFORMING NVH DIAGNOSTIC TESTS.

2034-91_0103

1. j���&����$����+��������@������$�/�����$����+&����:�*�K�� $������@����$��Z&��������&���+��$��

formulas, and determine the universal joint operating angles and driveline cancellation angle.

2. What is the transmission output shaft angle?

3. What is the axle input angle?

4. What is the propeller shaft angle?

5. What is the propeller shaft cancellation angle?

20 Noise, Vibration, and Harshness

#�������������������$��%�&�������'������ ���

Notes:

Noise, Vibration, and Harshness 21

��������&"���'������ ��

ACTIVITY 10 CHASSISEAR DEMONSTRATION

Observe the instructor’s demonstration on the use of the ChassisEAR and answer the following

questions.

1. What do you hear when listening to the fuel injector through the ChassisEAR?

2. What do you hear when listening to the fuel line through the ChassisEAR?

3. What do you hear when listening to the rear axle through the ChassisEAR?

4. Do you think there is an excessive amount of whining noise from the rear axle? Why or why

not?

5. What do you hear when listening to the generator through the ChassisEAR?

6. Do you think there is an excessive amount of whining noise coming from the generator?

Why? or Why not?

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Copyright 2012 Chrysler Group LLC. All rights reserved.

UNITED STATES AND CANADA

MILLER SPECIAL TOOLSBosch Automo ve Service Solu ons

MILLER SPECIAL TOOLSINTERNATIONAL

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BOSCH AUTOMOTIVE SERVICESOLUTIONS Pty Limited

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Tel: +81-3-5436-3610Fax: +81-3-5436-3621

Mitla No. 442Col. Ver z Narvarte03600 Mexico D.F.Tel: (52)55-25-95-16-30Fax: (52)55-25-95-16-39

BOSCH AUTOMOTIVE SERVICESOLUTIONS Corpora on (Japan)

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SPX CHINA

333 Fuquan Road North IBPChangning DistrictShanghai 200335 P.R. ChinaTel: +86 21 2218 2758Fax: +86 21 2218 2667

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BOSCH AUTOMOTIVE SERVICESOLUTIONS BRAZIL

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2011

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