Preinspection

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-joint. 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
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 (such as road speed, type of road, drive mode, engine temperature, ambient temperature, etc.) affecting the appearance and degree of the concern.

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.

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. If equipped with AWD, rear axle evaluations should be done on straight road sections.