On standard differential rear axle assemblies, use SAE 80W-90 GL-5 (SAE 80W GL-5 in Canada) gear lubricant. On limited slip differential rear axle assemblies, use 4 fl. oz. of limited slip differential additive lubricant and SAE 80W-90 GL-5 gear lubricant.
See Figure 1
The gear lubricant in the drive axle should be checked every 12 months or 15,000 miles (24,000km).
- 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
The rear axle should have the gear lubricant changed every 7,500 miles (12,000km). If equipped with a limited slip differential, be sure to add 4 oz. (118mL) of GM limited slip additive part No. 1052358.
- Raise the car and support on jackstands. Place a container under the differential to catch the fluid.
- Remove the bolts retaining the parking brake cable guides and position aside.
- Clean all dirt from the area around the cover. 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.
- With the cover and housing washed free of oil and gasket material, 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.
- Install the parking brake cable guides, if removed.
- The fluid level should reached a level within 3 / 8 in. (10mm) of the filler plug hole. Replace the filler plug. Lower the car and inspect for leaks.