Inspect for proper gear oil levels prior to performing system diagnosis.

Low gear oil levels

Fill axle to the recommended level.

Refer to Rear Axle Lubricant Replacement .

A low level may create intermittent or incomplete clutch park engagement.

Incorrect gear oil

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

Refer to Rear Axle Lubricant Replacement .

Incorrect gear oil may create improper clutch pack engagement or a slippage condition.

Worn clutch pack oil pump

Replace the clutch pack assembly.

Worn clutch pack friction discs

Replace the clutch pack assembly.