For 1990-2009 cars

Cause | Correction
--- | ---
Inspect for proper gear oil levels prior to performing system diagnosis.
Low gear oil levels | Faulty oil seal or other types of leaks may contribute to lower than required fluid levels. Refer to Rear Axle Lubricant Leak Diagnosis . Fill to the proper level with gear oil, GM P/N 12378514 (Canadian P/N 88901045). Refer to Rear Axle Lubricant Replacement .
Worn or loose axle mounts | Repair or replace axle mounts as required. Refer to Differential Housing Support Bushing Replacement .
Worn propeller shaft constant velocity or universal joints | Replace the universal joints as required. Refer to Propeller Shaft Replacement . If constant velocity joint is damaged, replace the propeller shaft. Refer to Propeller Shaft Replacement .
Worn propeller shaft center bearing assembly | Replace the center bearing assembly. Refer to Propeller Shaft Replacement .
Bearing noise within axle assembly | This type of noise will decrease or increase relative to the vehicle speed.

1. Check for the proper fluid level. Refer to Rear Axle Lubricant Replacement .
2. Repair or replace the unit as required.

Gear set whine noise within the carrier assembly caused by incorrect backlash | A whine type of noise will increase or decrease relative to the vehicle speed.

1. Check for the proper fluid level. Refer to Rear Axle Lubricant Replacement .
2. Repair or replace the unit as required.