For 1990-2009 cars

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Place a drain pan or suitable container underneath transmission.
3. Remove transmission oil level/filler plug from transmission (Two-Wheel Drive Models) (2).
4. Remove the transmission drain plug from the transmission and drain the transmission oil (Four-Wheel Drive Models) (3).
5. Remove transmission drain plug from transmission and drain transmission oil (Two-Wheel Drive Models) (3).
6. Apply GM P/N 12346004, or equivalent, to the threaded portion of the transmission drain plug (Four-Wheel Drive Models) (3).

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.

7. Install transmission drain plug (3) into the transmission (Two-Wheel Drive Models).

Tighten
Tighten the transmission drain plug to 28 N·m (20 lb ft).

8. Pour approximately 1.5 liters (1.6 qts) of synthetic 75W-90 GL4 lubricant, or the equivalent, into the transmission oil level/filler plug (2) hole. Oil level should be even with the bottom of the transmission oil lever/filler plug hole (Four-Wheel Drive Models).
9. Apply GM P/N 12346004 or the equivalent, to the threaded portion of the transmission oil level/filler plug (2).
10. Install transmission oil level/filler plug (2) into the transmission (Two-Wheel Drive Models).

Tighten
Tighten the transmission drain plug to 28 N·m (20 lb ft).

11. Install transmission oil level/filler plug (2) into the transmission (Four-Wheel Drive Models).
12. Remove the drain pan from underneath the transmission.
13. Lower the vehicle.