1. Driveline Diagnosis and Service
Chapter 76

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Problem Diagnosis Important terms Problems related to spider gears
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

14. 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

15. Axle Bearing Service Sealed rear axle bearings Repair of axle seal
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

16. 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

17. 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

18. Axle Bearing Installation and 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

19. 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

20. 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

21. 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

22. 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

23. Clean and Inspect Parts
Considerations
Look for signs of wear
Keep bearing caps with their bearings

24. 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

25. 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

26. 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

27. Contact Pattern Differential is adjusted Drive side of gear is convex
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

28. 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

29. 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

30. 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