Flow of Diagnosis

DESCRIPTION
Certain rear axle and driveline trouble symptoms are also common to the engine, transmission, rear wheel bearings, tires and other parts of the vehicle. For this reason, make sure the cause of the trouble is in the rear axle before adjusting, servicing or replacing any of its parts.

Certain trouble symptoms can be caused by limited slip differentials. Check the Vehicle Certification Label and axle ratio tag to determine the type of differential.

QUESTION THE CUSTOMER
The preliminary diagnosis begins with the service technician asking the customer diagnostic questions, especially for conditions of noisy operation or vibration.

Always ask the customer the following:
1. What is the exact nature of the symptom? If it is a vibration, how is it felt? If a noise, what kind? Is it high-pitched, a rumbling noise or some other concern?
2. What are the driving conditions in which the symptoms appear: road speed, drive or coast, on turns or on a grade only?
3. Is the condition constant or variable. Does a noise increase in pitch with speed or some other factor?

All information should be written on the service order so the technician will know where to start looking. The technician must be able to identify the axle concern from what is written on the order following the road test.

It is, of course, preferable to have the customer demonstrate the symptoms in a road test whenever possible.