Chapter 1 Introduction to Automatic Transmissions and Transaxles

After studying this chapter, you will be able to:� Explain the basic purpose of a transmission.� Identify the differences between manual and automatic transmissions.� Describe the differences between automatic transmissions and automatic transaxles.� Identify major automatic transmission and transaxle components.� Explain the basic operation of an automatic transmission or transaxle.� Trace the development of modern automatic transmissions and transaxles.

11

Technical Terms

Chapter 1

Introduction toAutomaticTransmissions andTransaxles

Gear ratio

Reduction gear

Direct drive

Overdrive

CV axles

Continuously variabletransaxles (CVTs)

Fluid couplings

Torque converters

Input shafts

Output shafts

Planetary gears

Holding members

Case

Oil pans

Bushings

Ball bearings

Hydraulic pump

Pressure regulator

Hydraulic control system

Electronic control system

Gaskets

Seals

Manual linkage

Throttle linkage

Transmission fluid

Transmission fluid cooler

Transmission fluid filter

Hybrid vehicle

Infinitely variable transmission (IVT)

Toroidal transmission

This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.

Introduction

Automatic transmissions and transaxles have beenused for more than 60 years. They have been consistentlymodified and improved, evolving from early inefficientdesigns to the smooth-shifting, efficient units of today.Most modern transmissions and transaxles are controlledby an onboard computer and provide almost the same fueleconomy as manual models.

To service late-model automatic transmissions ortransaxles, the technician must possess considerableknowledge and skill. This chapter will introduce you to thefundamentals of automatic transmissions and transaxles.The basic principles covered here will be expanded uponin later chapters.

The Purpose of Transmissions

All transmissions, whether manual or automatic, havethe same basic purposes:

� To transmit power from the engine to the drive wheelswhen necessary.

� To disconnect the running engine from the drivewheels during gear changes and when the vehicle isnot moving.

� To reverse the direction of power flow when the vehicle must be backed up.

� To multiply engine torque as needed.In simplest terms, a transmission modifies engine

torque and speed to match the vehicle’s needs. For exam-ple, moving a vehicle from a stop requires a great deal ofengine torque, or turning force. At low speeds, however,an engine produces relatively little torque. The transmis-sion must multiply engine torque to get the vehicle mov-ing. It does this by reducing speed to increase torque.

The relationship of the speed of the transmission’sinput shaft to the speed of its output shaft is called the gearratio. The transmission uses a set of at least two gears thatcause the output shaft speed to be much lower than theinput shaft speed. This set of gears is called a reductiongear. Figure 1-1 shows a simple reduction gear.

At higher speeds, the vehicle does not require asmuch engine torque to keep it moving. The engine wouldbe turning very fast if the transmission output speedremained slower than the input speed. High engine speedwill cause poor fuel economy and rapid engine wear.Therefore, the transmission must be shifted into succes-sively higher gears as vehicle speed increases. Shifting intohigher gears changes gear ratios, so the speed of the out-put shaft approaches and eventually equals or exceeds thespeed of the input shaft.

Most modern transmissions have at least four forwardgears, with the highest gear being either direct drive oroverdrive. A direct drive gear causes the input and output

shafts to turn at the same speed. The overdrive gear causesthe output shaft to turn faster than the input shaft, Figure 1-2.Overdrive allows the engine to turn at a relatively slowspeed, increasing fuel economy and reducing engine wear.

Both manual and automatic transmissions canaccomplish any of the previously mentioned jobs. Thereare many similarities between manual and automatictransmissions. All transmissions have a way of keeping theengine from stalling when the vehicle is stopped, all usegears and shafts to obtain different ratios, and all have away to reverse the direction of vehicle travel. However,with a manual transmission, the gear selection decisionmust be made by the vehicle’s operator. The driver slidesthe transmission gears in and out of engagement using agearshift lever. The gears are meshed in different combina-tions to achieve the desired gear ratios. The driver mustalso operate a manual clutch to connect and disconnectthe engine from the transmission when stopping or chang-ing gears.

12 Automatic Transmissions and Transaxles

3 Revolutions

Drive gear

90-tooth gear

Drivengear

Power out1 Revolution

30-toothgear

Power in

Figure 1-1. Gear reduction produces the torque needed tomove the vehicle from a stop. In this illustration, a 30-tooth gearis turning a 90-tooth gear. The 30-tooth gear must make threerevolutions to turn the 90-tooth gear once.This multiplies torquethree times but cuts speed to one-third.

30-toothdriven gear

3 ft-lb oftorque

Power in

90-toothdrive gear

1 ft-lb of torque Power out

Figure 1-2. In this example, overdrive is accomplished by usingthe 90-tooth gear to turn the 30-tooth gear. This increasesspeed three times but cuts torque to one-third.

With automatic transmissions, on the other hand, gearselection decisions are made by an automatic control sys-tem. Instead of a manual clutch to connect and disconnectthe engine from the transmission, automatic transmissionsuse fluid couplings or torque converters to transfer powerfrom the engine to the transmission.

Automatic transmissions use planetary gearsets,which do not slide in and out of engagement. In operation,one of the gears in the gearset is locked in place. Theremaining unlocked gears are driven by engine power andcomprise the input and output. Different gear ratios areachieved by different combinations of locked andunlocked gears. The gears are operated by holding mem-bers called clutches and bands. The clutches and bandsare controlled by a hydraulic control system. Late-modelautomatic transmissions have hydraulic systems controlled byon-board computers. Vehicles with automatic transmissionsare easier to drive than those with manual transmissions.They are also more durable for heavy-duty operation, suchas trailer towing. The major differences between manualand automatic transmissions/transaxles are shown inFigure 1-3.

The ideal transmission will transmit engine powerwith no slipping. Slipping can be defined as failure totransmit all engine power to the other drive train compo-nents. In other words, a slipping transmission will loseboth speed and torque between its input and output shafts.

Early automatic transmissions were so inefficient andslipped so much that they were called “slush boxes.”Modern automatics are efficient and smooth. Except forfirst and reverse gears, modern automatic transmissionspermit no slippage. They transmit as much engine poweras manual transmissions. It is now possible for an auto-matic transmission to be more efficient than a manual.With an automatic transmission, there is no need to releasethe accelerator pedal during shifts, and then reaccelerateto maintain vehicle speed.

Transmissions and Transaxles

Until about 20 years ago, nearly all vehicles had arear-wheel drive arrangement that used a transmission totransfer power to the rest of the driveline. The rear-wheel

drive transmission transmits power in a straight line, fromthe front of the vehicle to the back. The differential and thefinal drive assembly are contained in a separate housing atthe rear axle.

Today, most automobiles use front-wheel drive sys-tems equipped with transaxles. Transmissions andtransaxles perform the same function. The major differ-ences include the arrangement of the parts and the fact thatthe differential and the final drive assembly (sometimescalled the ring-and-pinion assembly) are an integral part ofthe transaxle. Transaxles have two output shafts, one foreach wheel. These shafts are attached to the CV axles.Engine power is transmitted sideways through a chain orgears at some point in the transaxle.

The advantages of transaxles include reduced weightand increased fuel economy. On trucks, however, weightand fuel economy are less of a factor than durability. Therear-wheel drive train is usually used on these vehicles.Therefore, it is important that both transmissions andtransaxles be understood completely.

Four-wheel drive vehicles have a transfer caseattached to the rear of the transmission. The transfer casesends power to the front wheels. Figure 1-4 illustrates thelayouts of modern rear-wheel drive vehicles with auto-matic transmissions and front-wheel drive vehicles withautomatic transaxles.

Automatic Transmission andTransaxle Development

The modern automatic transmission was not the resultof a single invention. Some components used in automatictransmissions were developed long before the automobileitself. Planetary gear principles were known during thetime of the Roman Empire and eventually appeared on theFord Model T. Fluid couplings were used to drive machin-ery in 19th century mills. The first automotive fluid coup-lings were used on English cars in the 1920s and onChrysler vehicles in the mid 1930s.

The 1938 Oldsmobile is widely considered the firstcar to have an automatic transmission. These earlyOldsmobile Hydra-Matics had planetary gears operated by

Chapter 1 Introduction to Automatic Transmissions and Transaxles 13

Transmission Function Manual Transmission Automatic Transmission

Driver operated clutch.

Sliding gears.

Sliding gears operated by driver.

Fluid coupling or torque converter.

Planetary gears.

Planetary gears operated by a hydraulic control system.

Engaging and disengaging engine drive wheels.

Reversing directions.

Changing gear ratios to match vehicle speed.

Figure 1-3. Although their basic function is the same, there are differences between automatic transmissions and manual transmissions.

a hydraulic control system. However, they used a manualclutch in place of a fluid coupling. The clutch was used toengage the transmission when the vehicle was first started,after which the hydraulic system made all the shifts.Figure 1-5 shows this early design. In 1939 (1940 models),Oldsmobile introduced an updated version of this transmission,replacing the clutch with a fluid coupling. Cadillac beganusing this transmission in 1940. This was the first fullyautomatic hydraulic transmission. See Figure 1-6.

The first transmission to use a torque converterinstead of a fluid coupling was the 1948 Buick Dynaflow,Figure 1-7. This transmission relied entirely on a complextorque converter with multiple stators and turbines fortorque multiplication. Although the torque converter pro-vided a much more efficient transfer of power than a fluidcoupling, the Dynaflow had no gear changes, and theplanetary gears were always in direct drive. The planetarygears were also used for manual low and reverse. TheDynaflow was smooth but extremely inefficient.

The first transmission that resembled modern trans-missions was designed by Ford and Borg-Warner andoffered in 1950. It used a torque converter and a hydrauliccontrol system that automatically changed gears. The firstmodels were two-speed types, while later designs hadthree speeds. A similar Borg-Warner transmission appearedon Studebakers. The Studebaker transmission, as well asone offered by Packard, contained the first version of thelockup torque converter, which eliminated slippage in certaingears. See Figure 1-8. The Studebaker automatic was thefirst to use a one-way clutch to obtain different gear ratios.

At first, all automatic transmissions had cast ironcases. Aluminum bell housings and tailshaft housingswere used on some Ford and Chrysler transmissions duringthe 1950s. The first transmission to use an all-aluminumcase was the Chevrolet Turboglide installed in the 1958models, Figure 1-9. The Chrysler Torqueflite followed in1960. All automatics were being designed with aluminumcases by 1965. Around this time, simplified gear trainswere introduced, some with only two forward gears. Alate-1960s transmission might have fewer than half theparts of a comparable model produced ten years earlier.

The Chrysler Corporation reintroduced the lockuptorque converter in 1977. It was controlled by hydraulicpressure, and the lockup clutch applied only in third gear.Later lockup torque converters were operated electricallyor electronically. Lockup clutches were applied in all gearsbut first and reverse.

In the early 1960s, a few vehicles, such as the Corvair,Volkswagen, and Porsche, used rear engines and wereequipped with transaxles. A few imported front-wheeldrive cars had transaxles. However, the front-wheel driveautomatic transaxle was unknown in the United Statesuntil the introduction of the 1966 Oldsmobile Toronado.The Toronado’s engine was mounted longitudinally (facingforward), and its transaxle used a conventional cast irondifferential bolted to the transmission case. In 1976,


Front ofvehicle

Engine

Torqueconverter

Transmission

Drive shaft Rear drive axles

DifferentialassemblyA

Front ofvehicle

Torqueconverter

Engine

Front drive axlesTransaxle

Rear dead axle

B

Engine

Frontdifferential

Front ofvehicle

Drive shaft

Drive shaft

Transfer case

Rear differentialRear drive axles

Transmission

Torqueconverter

Front drive axles

C

Figure 1-4. Various automotive drive trains. A—Rear-wheeldrive vehicle with a longitudinal engine and a transmission.B—Front-wheel drive vehicle with a transverse engine and atransaxle. C—Four-wheel drive vehicle with a transmission anda transfer case.


Manual control lever

Control shaft

Steering wheeland column

Acceleratorcross shaft

To carburetorClutchshaft Head gear set

Governor

Throttle controlhydraulic relay

Throttle controlledcompensator valve

Manualvalve

Front unit valve

Front servoRear servo

Rear planetary unit

Front planetary unit

Secondary oil pump

Primary oil pump

Pressure regulating valve

Main shaft

Figure 1-5. Diagram of an early Oldsmobile automatic transmission. A clutch was used to engage the transmission when the vehicle was started from a stop.

Figure 1-6. Cross-section of a Cadillac Hydra-Matic transmission. This transmission used a fluid coupling instead of a clutch.

Honda and Nissan introduced the first transverse (side fac-ing) engine and transaxle combinations sold in the U.S. By1980, all domestic manufacturers were producing front-wheel drive cars with transaxles. At present, almost all pas-senger cars use front-wheel drive and a transaxle. Manymodern transaxles use a belt and pulley mechanism tochange gear ratios. These transaxles are called continuouslyvariable transaxles, or CVTs.

The first attempt to use electricity to control the trans-mission was made in 1963, with the introduction of an

electric passing gear solenoid on the Pontiac Tempest,Figure 1-10.

Electric passing gears were used on other transmis-sions during the 1960s, and some electrically operatedlockup torque converters were used during the 1970s.When the first computerized engine controls were intro-duced, the transmission was often equipped with pressureswitches to tell the computer when the transmission was inhigh gear. During the 1980s, the power of on-board com-puters increased to the point that they could apply the


Variable pitch stator

Figure 1-7. Dynaflow transmission. Note the variable-pitch stator. Opening the throttle changed the angle of the stator blades forincreased torque during rapid acceleration.

Torque converterlockup clutch

One-wayclutches

Figure 1-8. Cross-section of a Studebaker automatic transmission.

converter clutch. Later they were able to control transmis-sion shifting and internal pressures. Early electronic trans-missions were simply updated hydraulic models, with onlya few functions being performed by the computer and theoutput solenoids. Modern transmissions and transaxles arefully controlled by the computer.

Automatic Transmission andTransaxle Components

Automatic transmissions are made of many separatecomponents and systems. See Figure 1-11 and 1-12. Someof the most important automatic transmission and transaxlecomponents are discussed in the following sections. Thesecomponents will be covered in more detail in later chapters.

Fluid Coupling/Torque Converter

Fluid couplings and torque converters are fluid-filledunits installed between the engine’s crankshaft and thetransmission. They consist of two sets of blades. One set ofblades is driven by the engine, and the other set of bladesis connected to the transmission’s input shaft. The blade setconnected to the engine is called the impeller, and theblade set connected to the input shaft is called the turbine.See Figure 1-13. A hydraulic pump in the transmissionforces fluid into the converter. Inside the converter, thefluid is spun by the impeller blades. As the fluid is thrownfrom the impeller blades, it strikes the turbine blades. SeeFigure 1-14. Power is transmitted from the impeller to theturbine through the fluid. When the vehicle is stopped, thefluid from the impeller continues to strike the turbine, butthe fluid allows enough slippage between the impeller andthe turbine to prevent engine stalling.


Passing gearsolenoid switch

Figure 1-9. 1958 Chevrolet Turboglide transmission. This trans-mission used an all-aluminum case.

Figure 1-10. A linkage-mounted switch energizes the passinggear solenoid on a 1963 Pontiac Tempest.

Flexplate Shiftlever

Oilpan

Valve body(hydraulic

control valves)

Case

Outputshaft

Drivelineslip yoke

Extensionhousing

Planetary gearsets

BandsClutches

Input shaftCrankshaft

Torque converter Converter housing

Engine

Figure 1-11. This diagram shows the major components of an automatic transmission. Note how the components fit in relation to each other.

The fluid coupling was widely used on early auto-matic transmissions. Fluid couplings, however, slip exces-sively and are very inefficient at transmitting power at lowspeeds. Therefore, fluid couplings have been replaced bytorque converters. In addition to an impeller and a turbine,a torque converter uses a device called a stator. The statorredirects the fluid to reduce slipping, Figure 1-15. Alltransmissions made since the 1960s use torque converters.

Modern transmissions are equipped with lockuptorque converters. These torque converters are equippedwith an internal clutch called a converter lockup clutch.The converter lockup clutch locks the transmission inputshaft to the converter cover. The clutch is applied to lockthe turbine to the cover. Since the input shaft is attached tothe turbine, slippage is eliminated. The lockup clutch isdisengaged at low speeds to prevent engine stalling.


Inputshaft

Torque converter

Converterhousing

Pump andreactor support

Pumpgasket

Selective thrust washers Intermediateband

Output shaft hub and ring

gear assembly

Reverse planet

Sun gear

Input shell

Front planet

Reversehigh clutch

Forwardclutch

Forward clutch hub and ring

gear assembly

Throttle valve

Remove asassembly

Low-reversedrum

Low-reverseband

Innerrace

Rollers

Cage spring

Outer race

One-way clutch

CaseLow-reverse

servo

TV rod Diaphragm

Collectorbody

Governor

Distributorsleeve

Park gear

Parking pawland spring

Vent capOutputshaft

Valvebody

Filterscreen

Extensionhousing

and gasket

Pan gasket

Oil pan

Figure 1-12. Exploded view of a typical automatic transmission. (Ford)

Input and Output Shafts

All transmissions have input shafts and output shafts.For strength, the shafts are made of heat-treated steel. Theshafts are splined to attach to other parts of the transmis-sion for power transfer. Every transmission must have sep-arate input and output shafts, Figure 1-16 and 1-17. Most

automatic transaxles have at least one hollow shaft. Thesolid shaft can turn inside the hollow shaft to permit powertransfer to each side of the vehicle. See Figure 1-18.

Planetary Gears

Planetary gears are used in all automatic trans-missions and transaxles. The term planetary comes fromthe resemblance of the gear assembly to the solar system.The basic planetary gear consists of a central sun gearsurrounded by planet gears that are housed in a planetcarrier. A ring gear with internal teeth surrounds the sunand planet gears. Figure 1-19 shows the main parts of aplanetary gear assembly. The advantage of the planetarygear is that the gears remain in mesh at all times. Thisprevents gear clash when shifting. Different gear ratioscan be obtained by holding or driving different parts ofthe planet gear assembly. Simple planet gears can becombined into more complex units, such as the oneshown in Figure 1-20. Complex planetary gear sets areused to obtain many gear ratios.

Holding Members

Holding members are the units that hold or drive thevarious parts of the planetary gear assembly to drive thevehicle. Holding members consist of friction material,which is similar to that used on manual clutches or brakeshoes, bonded to a metal backing. Clutches and bands arethe most common holding members. Clutches are a seriesof flat, ring-shaped plates.


Turbine Impeller

Impeller

Transmissioninput shaft

(driven shaft)

Crankshaft(driving shaft)

Stator

Turbine

Converter cover

Figure 1-14. Engine power flows from the pump, or impeller, to the turbine. The impeller causes the fluid to rotate. Then, the fluidcauses the turbine to rotate. Following the arrows, you will notice that the fluid returning from the turbine strikes the impeller in theopposite direction of impeller rotation. (General Motors)

Figure 1-13. This sectional view of a torque converter showsthe three main parts: the impeller, the turbine, and the stator. Allmodern converters have these three parts arranged in this way.Modern converters also contain an internal clutch to eliminateslippage.

They are applied (pressed together) by a hydraulicallyoperated clutch piston, or apply piston. The clutch platesare alternately splined, and applying them holds two partstogether. One set of plates is lined with friction materialand the other set is bare steel. Clutches are commonly

used to deliver engine power to the planetary gears, andhold parts of the gear assembly to the case. The entireassembly of clutch plates, the apply piston, and related


Turbine

Stator not turning

Converter multiplying,stator reversing oil flow

from turbine

Impeller

Figure 1-15. The stator reverses the flow of the fluid leaving the turbine. The fluid then strikes the impeller in the same direction asimpeller rotation. This multiplies engine power. (General Motors)

Bushings

Inputshaft

Output shaft

Bushing

Stator support

Outer shaft

Inner shaft

Figure 1-16. The input and output shafts are installed at thecenterline of the transmission, but they are not connected. Theinput shaft is splined to the converter turbine. The output shaftis splined to the final drive unit. Connecting the input and output shafts is the job of the other transmission components. (Ford)

Figure 1-18. Some shafts are hollow to permit other shafts torotate inside them. Hollow shafts are commonly used ontransaxles.

Figure 1-17. Typical output shaft.

components is called a clutch pack. A typical clutch packis shown in Figure 1-21.

Bands wrap around drums (cylindrical transmissionparts) to hold them stationary. The band is tightenedagainst the drum by a hydraulic piston called a servo,which is operated by hydraulic pressure. Figure 1-22shows a band, servo, and related linkage.

Another type of holding member is the one-wayclutch, Figure 1-23. A one-way clutch is a mechanicaldevice that allows the central hub to turn in one direction,but causes it to lock up when it tries to turn in the opposite

direction. One-way clutches are always used in combina-tion with other holding members to hold or drive parts ofthe planetary gearsets.

Case and Housings

The case is the main support for the other transmis-sion or transaxle parts. It also contains passages to deliverpressurized fluid between various parts of the transmission.Modern cases are made of aluminum that is cast into theproper shape. After casting, the case is machined wherenecessary to form mating surfaces for the other compo-nents. Oil passages are then drilled in the case where nec-essary. Bushings may be pressed into the case at wearpoints. Figure 1-24 shows two common transmission andtransaxle cases. On most modern vehicles, the housingsaround the torque converter and the output (or tail) shaftare cast as an integral part of the case. When used, sepa-rate bell housings (housing around the torque converter)and tailshaft housings are bolted to the case.

Oil Pans

All transmissions or transaxles contain one or moreoil pans. The main purpose of the oil pan is as a storageplace for extra transmission fluid. Airflow over the oil panhelps remove heat from the fluid. Some oil pans contain a


Planet gearsand carrier

Sun gear

Internal gear

Figure 1-19. This figure illustrates the three main components of a simple planetary gearset: the sun gear, planet gears and planet carrier, and the internal, or ring, gear. (General Motors)

Figure 1-20. Simple planetary gears can be combined into mul-tiple, or compound, gearsets to obtain many different gears.This photograph shows a gearset containing two sun gears,two planet carriers, and a ring gear. Many other combinationsare possible.


Retainingring

Clutchfriction plates

Clutchcylinder

Compressionrings (20)

Retaining ring

Steel clutch platePressure

plateLugs matewith input

shell

Hydraulic pistonwith O-rings

Compression spring retainer

Retainer snap ring

Cover O-rings

Servo cover

Piston seals

Piston

Snap ring

Return spring

Cushion spring

Piston rod

Band assembly

Lining

Pin

Anchor strut

Band ends

Drum and forwardsun gear assemblyNote: Sun gear is

inside drum

Band servoassembly

Figure 1-21. This exploded view of a multiple disc clutch shows all the components that make up a common clutch pack. Clutchpacks can be used to transmit power or to lock parts of the gear train to the case. (Ford)

Figure 1-22. The band and servo shown here are used to grab a drum and stop it from turning. Bands are always used to lock apart of the gear train to the case. (Subaru)

magnet to trap the metal particles produced as the trans-mission components wear. Oil pans are usually made ofsheet metal. A few pans are made of cast aluminum.

Bushings and Bearings

Bushings and bearings allow parts to move againsteach other with minimal friction. Bushings, Figure 1-25,provide a sliding contact with the moving part and requiregood lubrication. They are installed where rotating partpasses through a stationary part or two rotating parts are incontact with each other.

Ball bearings or roller bearings provide a rolling con-tact for reduced friction. Bearings are usually used wherethere is a heavy load, such as the output shaft, or an inter-nal part that is subjected to high pressure. Thrust bearings

are used in other places where parts are rotating in relationto each other under heavy pressures. A thrust washer sep-arates moving parts, but it is made of a single piece of flatmetal. Some thrust washers are available in differentthicknesses and are used to adjust transmission shaft back-and-forth movement, or endplay. Typical roller bearings,thrust bearings, and washers are shown in Figure 1-26.

Hydraulic Pump and Pressure Regulator

The hydraulic pump provides all the hydraulic pres-sure used in the automatic transmission or transaxle. Anextension at the rear of the torque converter drives thepump on transmissions. A separate shaft attached to theconverter is often used to drive transaxle oil pumps.Whenever the engine is running, the converter is turningand causing the pump to turn. Therefore, whenever the


Figure 1-23. A one-way clutch assembly. Note how each rollerfits into a ramp on the inside of the outer gear. This design permits the internal roller to rotate in one direction but locks itwhen it tries to turn the other way.

Figure 1-24. Common transmission and transaxle casedesigns are shown here. Power enters the transmission case atthe front and exits at the rear. Power enters the transaxle case atthe engine connection and exits in two directions. A fewtransaxles are designed so power exits in only one direction.

Figure 1-25. The average transmission or transaxle contains many bushings to support moving parts. Bushings may be installedbetween the case and a moving shaft, or between two turning parts. (General Motors)

engine is running, the pump is producing pressure. Thereare several types of hydraulic pumps. These will be dis-cussed in a later chapter.

The hydraulic pump draws transmission fluid from thebottom or side oil pan, which is usually called the sump.The pump pressurizes the fluid for use by the otherhydraulic system components, Figure 1-27. Moderntransaxles with two oil pans may have more than onepump. In systems that contain three pumps, a three-gearscavenger pump removes the fluid from the bottom panand pumps it into the side pan. The primary and secondarypumps pick up the oil from the side pan and pump it tothe other hydraulic system components. On very old

vehicles, a pump was installed on the output shaft and itproduced pressure only when the vehicle was moving.Output shaft pumps are no longer used.

The pressure regulator is installed in the outlet linefrom the pump and controls overall transmission pressures,usually called line pressures.

If the pump output becomes too great, the pressureregulator valve opens, dumping oil back into the oil pan.Once the pressure returns to normal, the valve closes. Apressure regulator is shown in Figure 1-28. The pressureregulator may be installed in the pump housing or in thevalve body.


MN 7models

Roller bearings

Rollerbearing

Thrustwashers

Thrustbearings

Thrust washers

Rollerbearings

Thrustbearing

Thrustbearing

Rollerbearing

Figure 1-26. Modern transmissions and transaxles contain many bearings. Some bearings are round types that serve the same pur-pose as bushings. Others are flat rings that keep moving parts from rubbing against each other. (General Motors)

Hydraulic Control System

The hydraulic control system is a set of hydraulicparts and passages that performs the following functions:

� Applies and releases the holding members to obtainthe needed gear ratios at any vehicle speed and throt-tle position.

� Controls system pressures for proper shift feel andlong holding member life as loading and accelerationvary.

� Keeps transmission fluid flowing to the torque con-verter, transmission cooler, and lubricating system.

The major component of the hydraulic control sys-tem is the valve body, which contains the control valvesand related springs. The valve body also contains themanual valve, which is connected by linkage to the shiftlever in the passenger compartment. Moving the manualvalve directs pressure to other parts of the hydraulic sys-tem. The valve body may also contain accumulators,check balls, and spacer plates. A typical valve body isshown in Figure 1-29. Other parts of the hydraulic systeminclude governor valves, throttle linkage, band servos,clutch apply pistons, and the passages that connect them.Some of these passages and parts may be located in thetransmission case.

Most modern transmissions and transaxles use anelectronic control system to operate the hydraulic com-ponents. An on-board computer processes informationfrom input sensors. It then uses this information to operatesolenoids and other output devices installed in the trans-mission or transaxle to control pressure flow through thehydraulic system. See Figure 1-30. Figure 1-31 illustratesthe input and output devices used with a typical electron-ically controlled transmission. The construction and oper-ation of hydraulic and electronic control components willbe discussed in detail in later chapters.

Gaskets and Seals

Gaskets and seals are used to keep fluid from leakingout of the transmission or transaxle and to keep pressurefrom leaking internally. Gaskets are used where majorcomponents are joined together. For example, a gasket isused to seal the oil pans to the case. Gaskets are also usedin the valve body and where the front pump and extensionhousing are attached to the case. See Figure 1-32.


Drivengear

Crescent

Drive gear

Vacuum

Atmosphericpressure

Inlet

Fluidsqueezed

out

Outlet

To system

Oil sumpscreen

Sump

Spring

Valve

To oil pan onpump intake To rest of

hydraulic system

To oilpump

Boost pressure from other

transmission valves

Figure 1-27. Simplified hydraulic pump. Fluid is drawn in as thegears move apart. It is then carried around by the gear teethand pressurized as the teeth come together. (Ford)

Figure 1-28 . Simplified pressure regulator. If system pressurebecomes too great, the valve moves against spring pressureand oil is routed back to the oil pan.

Manual valve

Valve body

Solenoid

Connector

Wiring harness

Figure 1-29. Valve bodies contain the hydraulic valves, checkballs, springs, restrictors, screens, and other componentsneeded to control the holding members. Note that this valvebody uses electrical solenoids to control transmission operation.

Seals are used at moving parts, such as the torqueconverter, drive shaft, and various internal rotating parts.They are also used as sliding pressure seals at the band ser-vos and clutch apply pistons. Figure 1-33 shows a servoseal. Some seals are used to seal stationary parts. Theseseals are usually called O-rings.

A seal ring is a special type of seal that prevents leaksin pressure passages between parts that rotate in relation toeach other, Figure 1-34. For example, oil pressure from thevalve body may be directed through a stationary support toa rotating clutch drum. Seal rings keep the pressure frombeing lost.

Manual Linkage and Throttle Linkage

To provide drive input, two types of linkage are used.The manual linkage connects the shift lever to the manualvalve inside the transmission or transaxle. The linkage can bea cable or a series of rods and levers. Cables are commonly

used on modern vehicles. Figure 1-35 shows a commonlyused manual linkage arrangement. The shifter is mountedon the steering column or on a center console. In the Parkposition, the manual linkage operates a park lock insidethe transmission or transaxle. The park lock is a lever thatengages a toothed wheel on the output shaft, Figure 1-36.When the park lock is engaged, the vehicle cannot roll.

Throttle linkage connects the engine’s throttle plate tothe transmission’s throttle valve. On some transmissions,throttle linkage is used to apply extra pressure for a forceddownshift (or passing gear). On other transmissions andtransaxles, the throttle linkage controls all shift speeds. Onsome older cars, a vacuum modulator controlled shift speeds.Vacuum modulators are still used on a few vehicles. Mostmodern throttle linkage is cable operated, Figure 1-37. Onnewer vehicles, the computer controls shift speeds andthrottle linkage has been eliminated.


TFP manual valve position switch

assembly

1-2 and 2-3 shiftsolenoid valves

1-2 and 2-3 shiftsolenoid valves

Output speed sensor

Input speed sensorPressure control

solenoid

TCC controlPWM solenoid

Figure 1-30. Sensors and solenoids used on a modern electronically controlled transaxle. The sensors provide input signals to thecomputer, which in turn sends output signals to the solenoids. (General Motors)

Transmission FluidTransmission fluid is a combination of petroleum oils

and various additives. It is pressurized by the pump andused to operate the hydraulic system. Since the trans-mission fluid splashes on the holding members, it containsadditives that help the holding members to grip when theyare applied. Transmission fluid also lubricates gears, bear-ings, and moving parts. Some transmission parts are lub-ricated by fluid under pressure. Other components dependon splash lubrication. Transmission fluid also carries awayheat and helps seal in pressure.

There are several types of transmission fluid used inmodern vehicles. Proper fluid is important to transmissionand transaxle operation. At one time, almost all automatictransmissions and transaxles used the same type of fluid.Today, however, many domestic and imported vehicles use special fluids. Never add transmission fluid to anyautomatic transmission or transaxle without first findingout what type of fluid should be used. Some manufacturersallow the use of a common fluid, such as Dexron III, if aspecial friction modifier is added to the fluid.


++

–

–

Map/baro sensor

Air conditioningclutch (ACC)

Engine RPM sensor(RPM sensor)

(diesel engines)

Profile ignition pickup(PIP) from distributor

engine RPM (gasoline engine)

Brake on/off(BOO) switch

Programmablespeedometer/odometer

module (PSOM)

Manual levelposition (MLP)

sensor

Transmission oiltemperature(TOT) sensor

Vehicle speedsensor (VSS)

4x4 low(4x4 L)

Transmissionsolenoid body

–SS1–SS2–EPC–TCC–CCS

RABSspeedsensor

Rearanti-lockbrake module

Speedcontrolmodule

PSOMVSS (+)

PCMVSS (–)

Malfunctionindicator

lamp (MIL)

Transmission controlindicator lamp (TCIL)

Powertraincontrol module

(PCM)

Throttleposition (TP)

sensor

Input/output(1989-1991

model transmissions)(1992 and 1993 model

transmissions)

Figure 1-31. The computer that controls a modern transmission or transaxle is connected to many input sensors and output devices. In some vehicles, a single computer may be used to control the transmission or transaxle, the engine, and other systems. (Ford)

Transmission Fluid Cooler

Transmission and transaxle operation causes the fluidto get very hot. This heat must be removed to keep thefluid from breaking down and to keep the holding mem-bers from becoming so hot that they begin to slip and burn.

To accomplish this, the transmission fluid is pumpedthrough metal lines to a transmission fluid cooler in thevehicle’s radiator. In the cooler, the fluid gives up its heatto the engine coolant and then returns to the transmission.On most transmissions, the fluid goes directly from thetorque converter to the cooler. This is because the torqueconverter produces most of the heat generated by thetransmission, especially at low speeds. Figure 1-38 showsthe path of transmission fluid through the cooler and backto the transmission. A few vehicles use a separate direct-air cooler. Direct-air coolers are also available as add-onunits. A direct-air cooler is a single tube bent into one ormore U-shaped forms. These forms are surrounded by fins.The direct air cooler is installed ahead of the radiator. Airpassing through the cooler removes heat by direct contact.

Transmission Fluid Filter

All transmissions and transaxles produce some metalshavings and particles of friction material as they wear.Additionally, transmission fluid breaks down from heat andage. The aging fluid develops solid deposits, which circu-late in the fluid. The metal shavings, friction material par-ticles, and solid deposits must be removed from the fluidas it circulates through the hydraulic system. Failure toremove these impurities can result in sticking transmissioncontrol valves and worn parts.

The transmission fluid filter catches and removesthese impurities as the fluid passes through it. Some filtersare fine mesh screens. Most filters, however, are made offelt or filtration paper enclosed in a metal or plastic hous-ing. The filter is always installed on the suction side of thepump so it can remove impurities before they reach thepump and other hydraulic system components. The filter islocated in the bottom of the transmission or transaxle so itis always covered by transmission fluid, Figure 1-39. A fewtransaxles have two filters. Filters should be changed aspart of periodic transmission or transaxle maintenance.


Figure 1-32. Gaskets are used throughout every transmission and transaxle. Some gaskets seal internal pressure passages. Otherskeep fluid from leaking out of the unit. (General Motors)

Automatic Transmission Operation

The following is a brief discussion of how an auto-matic transmission operates. The principles discussed herewill be explained in more detail in later chapters.

When the engine is running and the transmission is inPark or Neutral, the pump produces pressure to keep thetorque converter filled. No holding members are applied,and no power reaches the planetary gears. The converterimpeller turns the turbine and input shaft, but the powerstops at the planetary gears. In Park, the parking gear holdsthe output shaft stationary.

When the transmission is placed in Drive, oil flowsthrough the manual valve to one or more holding mem-bers. The holding members apply, causing the planetary

gears to connect the input and output shafts. Engine powergoes through the converter impeller, through the turbineand input shaft, and into the planetary gears. It exits theplanetary gears and tries to turn the output shaft. If thebrakes are applied, the turbine, input shaft, and gears donot move. Fluid from the impeller striking the turbine cre-ates friction and heat, which is removed by the cooler inthe radiator. Once the vehicle starts moving, the planetarygears reduce input shaft speed and increase torque to getthe vehicle moving.

As vehicle speed increases, the hydraulic control sys-tem moves various valves to change which holding mem-bers are applied. This changes the rotation of the planetgears and shifts the transmission into a higher gear. Powercontinues to flow through the torque converter, input shaft,planet gears, and output shaft.

As vehicle speed continues to increase, other valvesmove to obtain higher gears until the transmission is at itshighest gear ratio. At some point, the control systemapplies the lockup clutch for increased fuel economy. Withthe lockup clutch applied, the impeller and turbine turn atthe same speed.


Low-reverseservo

assembly

Seal

Figure 1-33. Lip seals are used to seal band servos, such asthe one shown here, or to seal clutch pack pistons. Lip seals aremoved outward by pressure and provide a tighter seal with lessresistance than would be possible with O-rings.(DaimlerChrysler)

Pumpextension

Seal rings

Figure 1-34. Metal or Teflon® seal rings are used to seal pressure passages. Seal rings usually provide a seal betweenrotating and stationary parts. (General Motors)

Transmissionshifter cable

assembly

Steering columnignition lock

cable assembly

Figure 1-35. The shifter linkage is used to transfer the driver’sshift selection to the transmission or transaxle. It can be aseries of rods and links, or, as shown here, a cable arrangement. (Ford)

When the vehicle is brought to a stop, the control sys-tem again moves various valves to lower the gear ratios tomatch vehicle speed and engine load. The control systemreleases the converter lockup clutch as the vehicleapproaches the completely stopped position.

In Reverse, the manual valve sends pressure to theproper holding members. They apply and hold the plane-tary gears to place the transmission in Reverse. Power goesthrough the impeller, turbine, and input shaft to the plane-tary gears. The planetary gears reverse the direction ofrotation before delivering power to the output shaft.

Hybrid Vehicle Drivetrain Operation

Hybrid vehicles use more than one source of energyfor propulsion. A hybrid gas-electric vehicle uses both aninternal combustion engine and an electric motor-generator.The motor-generator is installed between the engine andthe transmission or transaxle. Some vehicles have twomotor-generators. Depending on driving conditions andthe type of hybrid, the vehicle can be moved by the engineonly, the motor-generator only, or both the engine and themotor-generator.

Figure 1-40 shows a motor-generator installed in atransmission case. A stationary field winding is attached tothe engine block and a rotor is attached to the enginecrankshaft. A large, high-voltage battery is installed in thevehicle body. An electronic control system operates themotor-generator for maximum efficiency. The motor-gener-ator can crank the engine, eliminating the need for starterand flywheel gears. When the internal combustion engineis running, the motor-generator can produce electricity to recharge the hybrid's batteries and power its electrical circuits. Some hybrid vehicles do not have a reverse gear, andthe motor-generator runs in reverse to back up the vehicle. Anoverrunning clutch keeps the engine from turning backwardwhen the vehicle is in reverse.

The two major classes of hybrid vehicles are fullhybrids and mild hybrids. The motor-generator on a fullhybrid moves the vehicle as long as the battery is chargedabove a certain preset level. If the battery charge fallsbelow this level, the engine starts and propels the vehiclewhile recharging the battery.

On a mild hybrid, the engine moves the vehicle.During operation, the mild hybrid's engine shuts off duringcoasting, braking, and complete stops. When the driverpresses the accelerator pedal, the motor-generator restartsthe engine. When the engine starts, it begins turning themotor-generator, which then functions as an alternator torecharge the vehicle's battery.


Parking gear

Planetary output gear

Parking pawl

Free Lock

Figure 1-36. The parking gear linkage is attached to the transmission/transaxle shifter linkage. Moving the linkage causes the park-ing pawl to engage the parking gear on the output shaft. (Subaru)

Carburetorlever

Valveassembly

TV link

TV cable

Throttle lever andbracket assembly

Cable adjuster

Figure 1-37. On many older vehicles, throttle linkage was usedto control shift speeds and transmission pressures. The linkagewas connected between the carburetor or throttle body and athrottle valve in the transmission. Increased throttle openingcaused the throttle valve to increase pressures in the trans-mission and to delay the upshift. (General Motors)

Future Transmissions

Transmission technology is always advancing, andsome entirely new concepts are being developed. The fol-lowing section discusses transmissions that may appear infuture vehicles.

Toroidal or Infinitely VariableTransmission (IVT)

Figure 1-41 shows an infinitely variable transmission(IVT), also known as a toroidal transmission, that is cur-rently being used in Asia. This type of transmission mayeventually be installed in vehicles made for American andEuropean roads. The IVT consists of a set of movable discsthat rotate between drive and driven races. Varying theangle of the discs varies the speed ratio between the driveand driven races. Since sending power through the discsreverses the direction of rotation, a second set of movablediscs are installed behind the driven race. The driven racepowers a final output race through the discs. This againreverses power flow so that power exits the transmission inthe same direction as it entered. The combination of ratiosbetween the two sets of discs results in the final transmis-sion ratio.

The angles of the movable discs are varied by servosthat are operated by the transmission’s hydraulic system.An onboard computer monitors and adjusts the hydraulicsystem outputs based on inputs from engine and roadspeed sensors.


Automatictransmission

Linefittings

Lineclamp

Oil coolerinside radiator

Upper oil coolerfeed line

Lower oil coolerreturn line

Radiator

Figure 1-38. To cool the transmission fluid, an oil cooler is often installed in the vehicle’s radiator. Transmission oil pressure forcesfluid through the cooler, where it gives up heat to the engine coolant. The cooled fluid then returns to the transmission. Hot fluidusually comes directly from the torque converter, where most transmission heat is generated. (General Motors)

Transmissionhousing

Transmissionfilter

Oil pan

Figure 1-39. The transmission filter is located at the lowestpoint in the transmission, usually in the lower oil pan. Thisallows it to pick up transmission fluid, even when the fluid levelis slightly low. (General Motors)

Note: The motor-generator in some mildhybrids can move the vehicle if the enginefails.This allows a vehicle with an inoperable

engine to be driven to a service facility.

Electronically Shifted ManualTransmission

Many modern manual transmissions operate withouta clutch pedal. Electronically operated devices controlclutch operation and gear selection. The driver moves ashifter, or “paddle,” that sends signals to an onboard com-puter. The computer controls solenoids or motors to shiftgears and also applies and releases the clutch. On somevehicles with this type of transmission, the clutch pedal isused only to start moving the vehicle from rest. Other vehi-cles with electronically shifted manual transmissions haveno clutch pedal at all.

The transmission controls now in use can be con-nected to the engine and anti-lock brake computers. Thecomputers could provide fully automatic shifting. Somemanufacturers are working on automatic versions of man-ual transmissions. A few of these designs are being used inlarge trucks, usually with a torque converter replacing themanual clutch.

Dual Clutch Transmission

One type of electronically shifted manual transmissionthat may replace the planetary-type automatic transmissionon some vehicles is the dual clutch transmission, or DCT.It can be thought of as two manual transmissions, each withits own clutch, in one housing, Figure 1-42. In a five-speedDCT, one transmission contains the odd-numbered gears(first, third, and fifth) and the other transmission containseven-numbered gears (second and fourth). A reverse gearis built into one of the transmissions. To save space, thetwo transmissions and clutches are combined into a singleunit. Hollow shafts allow each transmission to transferpower without interfering with the other transmission.

Operation depends on alternately applying and releasingthe clutches, and engaging gears before the clutch isapplied. For instance, when the vehicle is accelerating infirst, power flows through the clutch and first gear of theodd-gear transmission. While power is traveling throughthe odd-gear transmission, second gear of the even-geartransmission has been engaged, but is not yet deliveringpower. To shift to second, the odd-gear transmission clutchdisengages and the even-gear transmission clutch engages.Power then flows through the clutch and second gear of theeven-gear transmission. Meanwhile, third gear of the odd-gear transmission is engaged for the next shift.

The vehicle powertrain computer controls gear selectionand clutch application sequence. This results in fast, smoothshifts, with no gear clash or interruption in power flow. Thepowertrain module is programmed to give the best shiftpattern at various throttle openings. DCT fuel efficiency isabout 15% better than that of a torque converter automatic.


Figure 1-41. Infinitely variable transmissions (IVTs), like theone shown here, are currently being used in Asia. In this IVT, aplanetary gearset provides reverse. (NSK)

Figure 1-40. This motor-generator is installed between theengine and transmission. Note the stator, rotor, and controlmodule. (ZF)

Figure 1-42. The clutches can be seen in this cutaway of a dualclutch transmission. Note the oil pump and cooler used to coolthe oil in the wet clutch.They are the only hydraulic componentsin the transmission. (ZF)


Summary

Manual and automatic transmissions have the samebasic purposes. They must connect and disconnect theengine and drive wheels, multiply engine power as dictatedby vehicle speed and load, and provide a way to reversethe direction of power flow.

Manual and automatic transmissions have many sim-ilarities. Major differences are that automatic transmissionsuse of a torque converter instead of a clutch, planetarygears instead of sliding gears, and a hydraulic control sys-tem that makes shifting decisions for the driver. Modernautomatic transmissions and transaxles are almost as effi-cient as manual models. Transmissions and transaxles dif-fer only in the layout of parts and the fact that the transaxlecontains the final drive assembly and the differential.

The modern automatic transmission has been gradu-ally refined over the years. The first automatic transmissionwas introduced more than 60 years ago. Over the years,automatic transmissions with torque converters, simplifiedgear trains, and aluminum cases were developed andplaced in service. Lockup torque converters, transaxles,and electronic control systems have been introduced andgradually perfected during the last 20 years.

Fluid couplings and torque converters are fluid-filledunits that contain a set of impeller blades driven by theengine and a set of turbine blades connected to the inputshaft. All modern transmissions use a torque converterinstead of a fluid coupling. Modern torque converters usea lockup clutch to eliminate slippage.

All transmissions and transaxles have separate inputand output shafts and planetary gears. A basic planetarygear consists of a central sun gear surrounded by planetgears that are housed in a planet carrier. A ring gear withinternal teeth surrounds the sun and planet gears. Simpleplanet gear sets can be arranged into complex gear units toobtain different gear ratios.

The parts of the planetary gear assembly are held or driven by holding members. Clutches and bands arecommon holding members that are operated by hydraulicpressure. One-way clutches are mechanically operatedholding members.

The transmission or transaxle case is the support forthe other parts of the transmission. It contains oil pressurepassages. The oil pan is a reservoir for extra fluid. Thehydraulic pump provides all the pressure used in the auto-matic transmission or transaxle. The pressure regulator isinstalled in the outlet line to the pump and controls over-all transmission pressures.

The hydraulic control system provides pressure to theholding members and determines when shifts shouldoccur. It also keeps transmission fluid flowing to the torqueconverter, transmission cooler, and lubricating system. Onmost modern transmissions and transaxles, an electroniccontrol system operates the hydraulic components.

Manual linkage connects the shift lever to the man-ual valve inside the transmission or transaxle. Throttlelinkage connects the engine’s throttle plate to the trans-mission’s throttle valve and controls shift speeds.

Transmission fluid is made of oils and various addi-tives. The fluid is pressurized, and it operates the holdingmembers. It also lubricates moving parts, carries awayheat, and helps seal internal parts. The proper fluid isimportant to transmission and transaxle operation.

To cool the transmission fluid, it is pumped from thetorque converter to a cooler in the radiator. A few vehicleshave direct-air coolers.

To remove debris from the transmission fluid, a filteris installed on the pump intake. Filters can be screens orsome other type of filtering material in a plastic housing.Filters should be changed periodically.

Automatic transmission operation varies from onegear to another. In Neutral and Park, no holding membersare applied and the power flow stops at the planetarygears. In Drive or Reverse, holding members apply andcause the planetary gears to connect the input and outputshafts. Engine power goes through the impeller, throughthe turbine and input shaft, and into the planetary gears.The hydraulic control system varies gear ratios by applyingand releasing different holding members.

Review Questions—Chapter 1

Please do not write in this text. Write your answers ona separate sheet of paper.

1. One of the primary jobs of any transmission is to dis-connect the engine from the _____ _____ when thevehicle is not moving.

2. Which of the following gears should be selected toobtain the best acceleration from stop?

(A) Reduction gear.

(B) Direct drive.

(C) Overdrive.

(D) Passing gear.

3. If the transmission output speed is more than the inputspeed, the transmission is in a(n) _____ gear.

4. Which of the following gears should be selected toobtain the best fuel economy?

(A) Reduction gear.

(B) Direct drive.

(C) Overdrive.

(D) Passing gear.

5. Briefly explain why placing an automatic transmission indrive with the brakes applied does not kill the engine.

6. Planetary gears are so named because they resemblethe _____ system.

7. Clutches and bands are examples of _____ _____.


8. The _____ _____ serves as a storage place for extratransmission fluid.

9. _____ are used to adjust transmission shaft endplay.

(A) Bushings

(B) Shim packs

(C) Thrust washers

(D) None of the above.

10. The hydraulic pump is driven by the _____ _____whenever the engine is running.

11. The governor, oil passages, and servos are part of the_____ control system.

12. An on-board computer operates the _____ control system.

13. The _____ _____ is a cable or a series or rods andlevers that connect the shift lever to the manual valve.

14. Transmission fluid _____.

(A) carries away heat produced in the transmission

(B) helps the holding members grip when they areapplied

(C) helps seal in pressure

(D) All of the above.

15. The transmission fluid filter is always located on the_____ side of the hydraulic pump.

ASE-Type Questions—Chapter 1

1. In any transmission, gears are used to do all the fol-lowing except:

(A) provide direct drive.

(B) disconnect the engine and drive wheels.

(C) reverse the vehicle.

(D) provide overdrive.

2. Technician A says early transmissions were inefficient.Technician B says a slipping transmission is an effi-cient transmission. Who is right?

(A) A only.

(B) B only.

(C) Both A and B.

(D) Neither A nor B.

3. Which of the following materials is most commonlyused to make modern transmission and transaxlecases?

(A) Cast Iron.

(B) Wrought Iron.

(C) Magnesium.

(D) Aluminum.

4. The planetary ring gear has _____ teeth.

(A) internal

(B) external

(C) internal and external

(D) no

5. Which of the following is not part of a clutch pack?

(A) Apply piston.

(B) Steel plates.

(C) Servo.

(D) Splined hub.

6. Technician A says bands are applied by servos.Technician B says bands wrap around drums. Who isright?

(A) A only.

(B) B only.

(C) Both A and B.


7. The modern transmission/transaxle case is made of_____.

(A) cast iron

(B) steel

(C) plastic

(D) aluminum

8. The hydraulic control system contains all the follow-ing components except:

(A) governor.

(B) parking lock.

(C) accumulators.

(D) valve body.

9. Technician A says gaskets seal moving parts.Technician B says that O-rings seal stationary parts.Who is right?

(A) A only.

(B) B only.

(C) Both A and B.


10. Available transmission oil cooler configurationsinclude all of the following except:

(A) in the radiator—factory installed.

(B) in the radiator—aftermarket.

(C) in front of the radiator—factory installed.

(D) in front of the radiator—aftermarket.

Documents

Chapter 1 Introduction to Automatic Transmissions and Transaxles