For 1990-2009 cars

1. Raise the vehicle. Support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.

Important: It is not necessary to remove the transfer case skid plate (2) in order to gain access to the transfer case drain plug (3). An access opening in the transfer case skid plate has been provided for wrench access as well as transfer case oil drainage.

2. Place a drain pan or suitable container underneath the transfer case.
3. Remove the transfer case oil level/filler plug (1) from the transfer case.
4. Remove the transfer case drain plug (3) from the transfer case and drain the transfer case oil.
5. Apply GM P/N 12346004, or the equivalent, to the threaded portion of the transfer case drain plug.

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.

6. Place the transfer case drain plug into the transfer case.

Tighten
Tighten the transfer case drain plug to 28 N·m (21 lb ft).

7. Add approximately 1.7 liters (1.8 qts) of 75W-90 GL4 the lubricant or equivalent, into the oil level/filler plug hole. The oil level should be even with the bottom of the oil level/filler plug hole.
8. Apply GM P/N 12346004, or the equivalent, to the threaded portion of the transfer case oil level/filler plug.
9. Place the transfer case oil level/filler plug (1) into the transfer case.

Tighten
Tighten the case oil level/filler plug to 23 N·m (17 lb ft).

10. Lower the vehicle.