© 2012 Delmar, Cengage Learning Driveline Diagnosis and Service Chapter 76
Dec 22, 2015
© 2012 Delmar, Cengage Learning
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
© 2012 Delmar, Cengage Learning
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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Clean and Inspect Parts• Considerations
– Look for signs of wear
– Keep bearing caps with their bearings
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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
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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
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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
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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
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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
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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
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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