Inspect for the proper transaxle and gear oil levels prior to performing system diagnosis. Refer to Transfer Case Fluid Replacement .

Low gear oil levels

Faulty oil seals or other type external leaks may contribute to lower than required fluid levels. Refer to Transfer Case Leak Diagnosis .

Fill to proper level with gear oil GM P/N 12378514 (Canadian P/N 88901045).

Worn propeller shaft constant velocity joints

Replace the propeller shaft assembly. Refer to Propeller Shaft Replacement in Propeller Shaft.

Worn bearing in the rear differential torque tube assembly

Replace the torque tube assembly.

Bearing noise within the transfer case

A "grinding" or "roar" type noise will increase or decrease relative to the vehicle speed.

1. Check for the proper fluid level. Fill as required.
2. If the noise continues, repair or replace the internal components as required.

Gear set "whine" noise within the transfer case

A "whine" type noise will increase or decrease relative to the vehicle speed, approximately 50-60 mph.

1. Check for the proper fluid level. Fill as required.
2. If the noise continues, repair or replace the internal components as required.

Contributing factors may include:

•	Incorrect backlash between the gear sets

•	Worn or damaged gear teeth

•	Transaxle assembly noise

•	Rear differential noise