Differential Assembly: Testing and Inspection
Driveline System
Special Tool(s)
Inspection and Verification
Certain axle and driveline trouble symptoms are also common to the engine, transmission, wheel bearings, tires, and other parts of the vehicle. For this reason, be sure that the cause of the trouble is in the axle before adjusting, repairing, or installing any new parts.
Driveshaft Center Universal Joint (U-Joint) and Constant Velocity (CV) Joint Inspection
Place the vehicle on a frame hoist and rotate the driveshaft by hand. Check for rough operation or seizure of U-joints. Install a new U-joint if there are signs of seizure, excessive wear, or incorrect seating. Place the vehicle on a frame hoist and rotate the driveshaft by hand. Check for rough operation or seizure of CV joint. Install a new driveshaft if it shows signs of seizure, excessive wear, or incorrect seating.
Driveshaft Center Bearing
Rotate the driveshaft by hand. If the bearing shows signs of roughness or is noisy, install a new driveshaft assembly.
Noise Acceptability
A gear-driven unit will produce a certain amount of noise. Some noise is acceptable and audible at certain speeds or under various driving conditions such as a newly paved blacktop road. Slight noise is not detrimental to the operation of the axle and is considered normal.
Preliminary Diagnosis
Question the Customer
The preliminary diagnosis starts with the customer interview. The history of the concern must be investigated: When was it first noticed? Did it appear suddenly or gradually? Did any abnormal occurrence coincide with or precede its appearance (such as pothole or curb impacts, minor collisions, etc.)? Were any repair procedures carried out or new parts installed? It is also necessary to know any special conditions affecting the appearance and degree of the concern, such as road speed, type of road, drive mode, engine temperature, ambient temperature, etc.
A gradual appearance of the concern indicates a deterioration of a component, such as tires, halfshafts or wheel bearings.
A sudden appearance of the concern could indicate a lost wheel balance weight or seized CV joint.
Road Test
A road test is mandatory for any customer concern of noise/vibration that is not verified by the on-hoist check of chassis components. The Vehicle Road Test Evaluation form is arranged to record the conditions heard or felt during this test.
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Part 2 Of 2:
The road test form lists four operating conditions or modes in which some axle noises come and go: DRIVE, CRUISE, COAST, and FLOAT.
Operate the vehicle in all four modes and record those in which the noise occurs. Write down the kilometers-per-hour (miles-per-hour) range at which both noise and vibration occur. If equipped with four wheel drive (4WD), rear axle evaluations should be done on straight road sections only with 4WD lock engaged. The transfer case has similar construction to the rear differential. Both components exhibit similar noise characteristics. Axle noise can originate from either the transfer case or the rear differential. Using frequency analyzer evaluate vehicle between 60 - 80 mph. The transfer case will have objectionable noise frequency above 600 Hz. Rear differential will be below 600 Hz.
Vehicle Road Test Evaluation Form
Analysis of Leakage
Clean up the leaking area enough to identify the exact source.
A plugged axle housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.
Make sure axle lubricant level is at least 3 - 5 mm (1/8 - 3/16 inch) below the bottom of the fill hole.
Axle Vent
A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent. If the vent cannot be cleared, install a new vent.
Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
^ Damaged seal.
^ Worn seal journal surface.
Any damage to the seal bore (dings, dents, gouges, or other imperfections) will distort the seal casing and allow leakage past the outer edge of the axle drive pinion seal.
The axle drive pinion seal can be torn, cut, or gouged if it is not installed carefully. The spring that holds the axle drive pinion seal against the pinion flange may be knocked out and allow leakage past the lip.
A new pinion flange must be installed if any of these conditions exist.
Metal chips trapped at the sealing lip can cause oil leaks. These can cause a wear groove on the pinion flange and pinion seal wear.
When a seal leak occurs, install a new seal and check the vent to make sure it is clean and free of foreign material.
Drive Pinion Nut
CAUTION: Make sure to install nut to correct torque specifications.
On some high-mileage units, oil may leak past the threads of the pinion nut. This condition can be corrected by installing a new nut and applying threadlock and sealer on the threads and nut face.
Differential Seals
CAUTION: When installing shafts, do not allow splines to contact seal during installation.
Half shaft pilot bearing housing seals are susceptible to the same kinds of damage as axle drive pinion seals if incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The seal journal surface must he free of nicks, gouges, and rough surface texture.
Analysis of Vibration
Few vibration conditions are caused by the rear axle. On a vibration concern, follow the diagnosis procedure unless there is a good reason to suspect the axle.
Tires
WARNING: Do not balance the wheels and tires while they are mounted on the vehicle. Possible tire disintegration/differential/halfshaft failure could result, causing personal injury/extensive component damage. Use an off-vehicle wheel and tire balancer only.
Most vibration in the rear end is caused by tires.
Vibration is a concern with modern, high-mileage tires if they are not "true" both radially and laterally. They are more susceptible to vibration around the limits of radial and lateral runout of the tire and wheel assembly. They also require more accurate balancing. Wheel and tire runout checks, truing and balancing are normally done before axle inspection.
Wheel Hub Flange Bolt Circle Runout
NOTE: The brake discs must be removed to carry out all runout measurements.
1. Position the special tool perpendicular to the wheel hub bolt, as close to the hub face as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub until the next bolt is contacted. Record the measurement and continue until each bolt is checked. The difference between the maximum and minimum contact readings will be the total wheel hub bolt pattern runout. The runout must not exceed 0.38 mm (0.015 inch).
Pilot Runout
1. Position the special tools as close to the hub face as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub one full turn and note the maximum and minimum readings. The difference between the maximum and minimum readings will be the total pilot runout. Pilot runout must not exceed 0.15 mm (0.006 inch).
Wheel Hub Face Runout
1. Position the special tool on the wheel hub face, as close to the outer edge as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub one full turn and note the maximum and minimum readings. The difference between the maximum and minimum readings will be the total face runout. The runout must not exceed 0.254 mm (0.010 inch).
Wheel Hub, Steering Knuckle Inspection
1. Remove the wheel and tire.
2. Position the special tool. Push and pull the wheel hub by hand and measure the wheel bearing play.
3. If the wheel bearing play exceeds specification, install a new lock nut.
4. Reset the wheel bearing play and install a new wheel hub if necessary.
Halfshafts, Rear Wheel
NOTE: Install new CV joints only if disassembly and inspection reveals unusual wear. While inspecting the boots, watch for indentations ("dimples") in the boot convolutions. Indentations must be removed.
^ Inspect the boots for evidence of cracks, tears, or splits.
^ Inspect the underbody for any indication of grease splatter near the boots outboard and inboard locations. This is an indication of boot/clamp damage.