For 1990-2009 cars

1. Raise the vehicle. Support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the rear axle housing oil level/filler plug (1) from the rear axle housing.
3. Inspect the rear axle oil level. The oil level should be even with the bottom of the rear axle housing oil level/filler plug hole. If the oil level is low and no oil leaks exist, adjust the oil using 80W-90 GL5 lubricant GM P/N 12345977 (Canadian P/N 10953482), or equivalent.

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

4. Install the rear axle housing oil level/filler plug into the rear axle housing.

Tighten
Tighten the rear axle housing oil level/filler plug to 43 N·m (32 lb ft).

5. Lower the vehicle.