For 1990-2009 cars

### Strategy Based Diagnostics

Review the system operations in order to familiarize yourself with the system functions. Refer to Differential Carrier Assembly Description. All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system condition. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer to Strategy Based Diagnosis.

### Visual/Physical Inspection

• | Inspect for aftermarket devices, which could affect the operation of the vehicle. Refer to Checking Aftermarket Accessories.

• | Inspect the easily accessible or visible system components for obvious damage or conditions, which could cause the symptom.

• | Check for the correct lubricant level and the proper viscosity.

• | Verify the exact operating conditions under which the concern exists. Note factors such as vehicle speed, road conditions, ambient temperature, and other specifics.

• | Compare the driving characteristics or sounds, if applicable, to a known good vehicle and make sure you are not trying to correct a normal condition.

• | Inspect for all-wheel drive activation and operation.

| Factors that may contribute to an inoperative rear differential include:

- | Low gear oil levels

- | Differential inoperative due to antilock brake system (ABS) function

- | Inoperative engine control module (ECM) and/or wiring system

- | A mini-spare or different size tire installed

- | A fluid over-temperature condition

- | An inoperative or "stuck" clutch pump check valve

- | A defective rear differential assembly

- | An inoperative transfer case assembly

• | Sometimes it might be difficult to judge whether the noise is coming from the propeller shaft or rear differential carrier assembly. Refer to Symptoms - Propeller Shaft.

### Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.

### Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

• | Symptoms - Propeller Shaft--Refer to Symptoms - Propeller Shaft.

• | Symptoms - Wheel Drive Shafts--Refer to Symptoms - Wheel Drive Shafts.

• | Symptoms - Vibration Diagnosis and Correction--Refer to Symptoms - Vibration Diagnosis and Correction.