SAE 80W or SAE 80W-90 GL-5 (SAE 80W GL-5 in Canada) gear lubricant is recommended.
See Figure 1
The gear lubricant in the drive axle should be checked every 12 months or 15,000 miles.
- Raise the car and support on jackstands as close to level as possible.
- Remove the filler plug from the side of the drive axle housing.
- If lubricant begins to trickle out of the hole, there is enough and you need not go any further. Otherwise, carefully insert your finger (watch out for sharp threads) and check to see if the lubricant is up to the edge of the hole.
- If not, add oil through the hole until the level is at the edge of the hole. Most gear lubricants come in a plastic squeeze bottle with a nozzle; making additions simple.
- Install and tighten the filler plug.
DRAIN AND REFILL
If equipped with limited slip differential, the rear axle should have the gear lubricant changed at the first 7500 miles; be sure to add 4 oz. of GM limited slip additive part No. 1052358.
If the vehicle is used for trailer towing, the gear lubricant should be changed every 7500 miles.
- Raise the car and support on Jackstands. Place a container under the differential to catch the fluid.
- Remove the bolts retaining the cover to the housing. Pry the cover from the differential housing and allow the fluid to drain into the catch pan.
- Clean and inspect the differential. With the cover and housing washed free of oil, apply sealer to the mating surfaces.
- Using a new gasket, install the cover and torque the bolts to 20 ft. lbs. (27 Nm) in a clockwise pattern to insure uniform draw on the gasket. Fill the differential with fluid through the fill plug and add limited slip additive, as required.
- The fluid level should reach a level within 3 / 8 in. of the filler plug hole. Replace the filler plug. Lower the car and inspect for leaks.