Wheel Hub: Testing and Inspection
Inspection and VerificationCertain axle and driveline concern symptoms are also common to the engine, transmission, wheel bearings, tires and other parts of the vehicle. For this reason, make sure that the cause of the concern is in the axle before adjusting, repairing or installing any new parts.
Driveshaft Center Universal Joint (U-Joint) and Constant Velocity (CV) Joint Inspection
With the vehicle in NEUTRAL, position it on a hoist. Rotate the driveshaft by hand. Check for rough operation or seizure of the U-joints. Install a new U-joint if there are signs of seizure, excessive wear or incorrect seating. Check for rough operation or seizure of the CV joint. Install a new driveshaft if it shows signs of seizure, excessive wear or incorrect seating.
Driveshaft Center Bearing
With the vehicle in NEUTRAL, position it on a hoist. 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 produces a certain amount of noise. Some noise is acceptable and audible at certain speeds or under various driving conditions, such as on a newly paved blacktop road. Slight noise is not detrimental to the operation of the rear drive 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, or minor collisions)? 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 or ambient temperature.
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 a 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.
The road test form lists 4 operating conditions or modes in which some axle noises come and go: DRIVE, CRUISE, COAST and FLOAT.
Operate the vehicle in all 4 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. The transfer case has similar construction to the rear drive axle. Both components exhibit similar noise characteristics. Axle noise can originate from either the transfer case or the rear drive axle. Using a vibration analyzer, evaluate the vehicle between 95-130 km/h (60-80 mph). The transfer case will have objectionable noise frequency above 600 Hz. Objectionable rear drive axle noise frequency will be below 600 Hz.
Analysis of Leakage
Clean up the leaking area enough to identify the exact source.
A plugged rear drive unit (RDU) housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.
Verify the RDU 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.
Drive Pinion Seal
Leaks at the drive pinion seal originate from the following causes:
^ Damaged seal
^ Worn seal journal surface
Any damage to the seal bore (dings, dents, gouges or other imperfections) distorts the seal casing and allows leakage past the outer edge of the drive pinion seal.
The drive pinion seal can be torn, cut or gouged if it is not installed correctly. The spring that holds the drive pinion seal against the pinion flange may be knocked out and allow fluid to pass the lip.
Metal chips trapped at the sealing lip can cause oil leaks. These can cause a wear groove on the drive pinion flange and result in pinion seal wear.
When a seal leak occurs, install a new drive pinion seal and check the vent to make sure it is clean and free of foreign material.
A new drive pinion flange must be installed if any of these conditions exist.
Drive Pinion Nut
CAUTION: Install the drive pinion nut to the correct torque specifications.
On some high-mileage vehicles, oil may leak through the threads of the drive 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 seals during installation.
Halfshaft pilot bearing housing seals are susceptible to the same types of damage as 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 be free of nicks, gouges and rough surface texture.
Analysis of Vibration
Few vibration conditions are caused by the RDU. For a vibration concern, follow the diagnosis procedure in Vehicle/Testing and Inspection unless there is a good reason to suspect the RDU.
Tires
WARNING: Do not balance the wheels and tires while they are mounted on the vehicle. Possible tire disintegration/RDU/halfshaft failure could result, causing personal injury/extensive component damage. Use an off-vehicle wheel and tire balancer only. Failure to follow these instructions may result in personal injury.
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 the 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 RDU inspection.
Wheel Hub Flange Bolt Circle Runout
NOTE: The brake discs must be removed to carry out the 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 is the total wheel hub flange bolt circle runout. The runout must not exceed 0.38 mm (0.015 inch).
Pilot Runout
NOTE: The brake discs must be removed to carry out the runout measurements.
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 is the total pilot runout. Pilot runout must not exceed 0.15 mm (0.006 inch).
Wheel Hub Face Runout
NOTE: The brake discs must be removed to carry out the runout measurements.
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 wheel hub one full turn and note the maximum and minimum readings. The difference between the maximum and minimum readings is the total wheel hub 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 end play. Make sure that no suspension movement is noted.
3. If the wheel bearing end play is greater than zero, install a new wheel bearing.
Halfshafts, Rear Wheel
NOTE: Install new CV joints only if disassembly and inspection reveals unusual wear.
NOTE: While inspecting the CV boots, watch for indentations in the boot convolutions. Indentations must be removed.
^ Inspect the CV boots for evidence of cracks, tears or splits.
^ Inspect the underbody for any indication of grease splatter around the inner and outer CV boots. This is an indication of boot/clamp damage.