Driveline Diagnosis and Service

© 2012 Delmar, Cengage Learning

Driveline Diagnosis and Service

Chapter 76


Objectives• Diagnose and repair universal joints• Remove and replace axle bearings and seals• Disassemble and reassemble a differential• Run a gear pattern and adjust a differential


Introduction• Driveline components

– Drive shaft and U-joints– Axles and axle bearings– Differential

• This chapter covers more than driveline service and repair procedures– Hydraulic press procedures for installing

bearings and other parts are described


Drive Shaft Diagnosis• Drive shaft problems result in noise or vibration

– Worn or rusted U-joints– Worn slip yoke– Bad center support bearing

• Causes of clunking sound when changing from acceleration to deceleration– Worn slip yoke splines– Bad extension housing bushing– Excessively worn U-joint– Problems in the differential


Drive Shaft Diagnosis (cont’d.)• Whining sound that varies with speed

– Worn center support bearing in a two-piece driveshaft

• Vibration– Bent driveshaft or a worn universal joint

• Driveshaft inspection considerations– Physical damage and loose joints– Rust at seals– Excess slip yoke movement – Indentation in tubing


Universal Joint Diagnosis and Service

• Universal joint begins to fail– Squeaking sound is often noticed

• Most common cause of U-joint failure – Grease has dried out

• Sharp, one-time click sound – Often occurs when vehicle direction is changed– Vibration can also occur


Drive Shaft Service• Steps to remove a drive shaft

– Mark drive shaft– Unbolt rear U-joint from differential companion

flange– Pry rear U-joint forward away from differential– Wrap tape around U-joint cups– On two-piece drive shaft: unbolt center support

bearing• When removed: oil will come out of transmission


Universal Joint Disassembly• Important considerations

– Remove any snap rings– There are three ways U-joints are commonly

disassembled• Most common is to use a bench vise• Many shops have a special universal joint tool• Some shops pound the joint out with a hammer

– Inspect the old U-joint for unusual wear• Problem with driveshaft angles can cause galling


Universal Joint Reassembly• Important steps and points

– Replacement U-joints usually have a zerk fitting• If U-joint doesn't have zerk fitting: be sure to check

that it has been packed with lubricant– Put bearing cup partially into yoke– Do not knock needle bearings out of position– Move joint back and forth to see that it is free– Install one snap ring before completing pressing

procedure– Some replacement U-joints use internal snap rings


Drive Shaft Installation• Installing a drive shaft that bolts

– Be sure universal joints fit exactly– Be sure all contact surfaces are clean

• Major steps– With transmission in neutral: slip yoke into

transmission– Align marks– Install rear U-Joint– Install retaining bolts


Two-Piece Drive Shaft Service• Center support bearing sometimes fails

– Seized bearing can tear away rubber mount– Drive shaft will wobble

• Bearing is pressed off and new one is pressed on– Be sure to press on the inside bearing race

• Two pieces of drive shaft are separated– Reassemble in phase


Differential and Axle Diagnosis and Service

• Differential gears on RWD– Rarely wear out

• Causes of damage to gears– Moisture and dirt– Abuse by driver

• Sometimes gear ratio change is desired– Requires disassembly


Problem Diagnosis• Important terms

– Drive, cruise, coast, and float• Problems related to spider gears

– Pinion gears too tight on shaft– Side gears too tight or too loose in differential

case– Excessive backlash between spider gears

• Lubricant leaks– Not usually an obvious problem


Axle Bearing Diagnosis• Damaged axle bearing

– Can result in fluid leak or bearing noise– Important considerations

• Driving the vehicle can sometimes pinpoint problem• Raise the vehicle after the road test• Have colleague run the engine with transmission

engaged• Carrier bearings and pinion bearings will make a

constant sound• Limited slip differentials can make a chattering

sound during turns


Axle Bearing Service• Sealed rear axle bearings

– No service interval• Axle removal is required• Presswork is usually done by parts business or

machine shop• Repair of axle seal

– Requires removal of axle from differential


Removing a Bearing-Retained Axle

• Major steps and considerations– Remove retaining plate

• Cover on back of differential must be removed prior to removal of a C-lock axle

– Remove lock bolt of pinion shaft• Shaft is pulled out

– Push axles inward• Allows C-locks to be removed

– Pry out old seal and apply lubricant to new seal– Support the axle


Axle Bearing Replacement• Axles with pressed-fit bearings

– Removed independent of backing plate• Pressed-fit bearing replacement

– Do not try to press bearing and retaining ring off at same time

• Bearing explodes during removal– Comparable to a grenade exploding


Axle Bearing Installationand Reinstall the Axle

• Key points– Cage and rollers should always be able to be

turned during installation– Retaining ring is often heated for easier assembly

• Pressed into place against axle bearing– Reinstall axle in housing and bolt on retainer– Be sure that the slot in the retainer aligns with the

oil return hole in the axle housing• Similar to oil return on clutch bearing retainer on a

manual transmission


Full-Floating Axle Service• Found on trucks and vans

– Three-quarter ton and larger• Axle bearings

– Located in hub and brake drum assembly• Major steps

– To remove drum: axle must be removed first– Install a new bearing seal– Retaining nut is tightened until it has little or no

clearance– Install axle and beveled washers


Differential Pinion Seal Replacement

• Important considerations– Maintain tension on pinion bearing crush sleeve

• Use a dial indicator torque wrench– Always use a long bar to hold yoke from turning– Use puller to remove flange– Remove seal with hammer and chisel– Lubricate new seal and install


Differential Repair and Removing a Third Member

• Identify differential– Look for an identification tag

• Usually under one of the nuts holding third member or cover

• Remove third member– Pull the axles– Remove all nuts from studs around third member– Remove washers– Be careful not to drop third member


Disassembling a Salisbury Axle• Major steps and considerations

– Requires removal of rear cover– Remove C-locks and axles– Mark side bearing caps– Pry caps and remove from axle housing– Remove drive pinion gear


Clean and Inspect Parts• Considerations

– Look for signs of wear– Keep bearing caps with their bearings


Differential Reassembly• Major steps and considerations

– Clean and coat all parts with oil– Replace ring and pinion as a matched set– Install ring gears perfectly flat– Heat ring gear to make it easier to install– Torque ring gear retaining screws


Adjusting a Differential• Ring and pinion must mesh with each other in

correct position – Incorrect position: noise and rapid wear may

result• Adjustments

– Pinion gear depth: measures how far the pinion gear extends into the differential housing

– Ring and pinion backlash: too little backlash can break a gearset after it expands


Side Bearing Preload• Bearings can fail if too tight

– Too loose: ring gear can move in case• Causes noise and wear

• Salisbury axle preload and backlash adjustments – Made with shims

• Installed by pounding them in– Separable third member

• Side bearing adjustment made with backlash adjustment


Contact Pattern• Differential is adjusted

– Gear pattern is taken off of ring gear teeth• Colored paste is painted onto gear teeth

• Drive side of gear is convex– Coast side is concave

• Pitch line – Runs through center of tooth

• Face is area above pitch line and flank is area below• Good pattern

– Tends to be toward the toe of tooth when tested


Backlash Pattern Change and Pinion Depth Pattern Change

• An increased backlash causes pattern on both sides of gear tooth to move higher on tooth face– Moving ring gear closer to pinion will reduce

backlash clearance• Altering pinion depth results in a different

pattern change than changing backlash clearance– When changing pinion depth: leave pinion seal

out until correct depth has been established


Pinion Bearing Preload and Ring and Pinion Noise

• Pinion bearings must be preloaded– Use a collapsible spacer to preload the bearings– Check amount of effort required to turn pinion

• Ring and pinion noise– Pattern is good but there is a gear howl

• Replace ring and pinion– Noise during acceleration

• Points to heavy heel contact– Noise happens when coasting in gear

• Pattern will be too heavy on toe


Four-Wheel-Drive Service and Repair

• Key points– Same as two-wheel-drive components except for

transfer case and front hubs• Before attempting to service transfer case: check

service manual• Mark both drive shafts at each end• Axles and locking hubs must be removed in order

to remove differential from axle housing• 4WD wheel hub has a pair of tapered roller wheel

bearings similar to those found on 2WD vehicles• 4WD axle is the same on inside as a 2WD axle

Documents

Driveline Diagnosis and Service