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

Low gear oil levels

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

Fill the oil to the proper level with GM P/N 12378261 (Canadian P/N 10953455).

Worn propeller shaft universal joints

Repair the propeller shaft, as required. Refer to Propeller Shaft Replacement .

Worn or loose propeller shaft center support bearing

Replace components, as required. Refer to Propeller Shaft Replacement .

Bearing noise within the transfer case

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

1. Inspect for the proper fluid level and fill, as required.
2. If the noise continues, replace the transfer case, as required.

Gear set whine noise within the transfer case

A whine type noise will increase or decrease relative to the vehicle speed.

1. Inspect for the proper fluid level and fill, as required.
2. If the noise continues, replace the transfer case, as required.

Contributing factors may include:

•	Incorrect backlash between the gear set

•	Worn or damaged gear teeth

•	Transaxle assembly noise

•	Rear differential noise