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

Loose propeller shaft mounting bolts

Tighten the bolts as required. Refer to Propeller Shaft Replacement in Propeller Shaft.

Loose torque tube bracket or a damaged bracket bushing

Tighten the bracket bolts or replace the bracket as required.

Incorrect gear oil

Replace with gear oil GM P/N 12378514 (Canadian P/N 88901045).