GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Drive Axle



Most gear oils come in a plastic squeeze bottle with a nozzle end, which makes adding lubricant simple. You can also use a common turkey baster for this job. Use only standard GL-5 hypoid-type gear oil--SAE 80W or SAE 80W/90.

On all models equipped with a posi-traction/limited slip differential, GM recommends that you use only special GM lubricant available at your local Buick, Oldsmobile or Pontiac parts department. Also, the standard GL-5 fluid with a limited slip additive can be used.


See Figure 1

The oil in the differential should be checked at least every 7,500 miles.

  1. Park the vehicle on a level surface and remove the filler plug from the front side of the differential.

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Fig. Fig. 1: Remove the filler plug to check the lubricant level in the rear axle.

  1. If the oil begins to trickle out of the hole when the plug is removed, the differential is full. If no lubricant trickles out, carefully insert your finger (watch out for sharp threads) into the hole and check that the oil is up to the bottom edge of the filler hole.
  3. If not, add oil through the hole until the level is at the edge of the hole. Torque the fill plug to 29 ft. lbs. (39 Nm).


See Figures 2, 3, 4, 5 and 6

There is no recommended change interval for the rear axle lubricant, but it is always a good idea to change the lube if you have purchased the vehicle used or if it has been driven in water high enough to reach the axle.

  1. Park the vehicle on a level surface and set the parking brake.
  3. Remove the rear axle filler plug on the front side of the differential housing.
  5. Place a large drain pan underneath the rear axle.
  7. Unscrew the retaining bolts and remove the rear axle cover. The axle lubricant will now be able to drain into the container.
  9. Clean all gasket mating surfaces. Using a new cover gasket and sealant, install the axle cover. Tighten the retaining bolts in a crisscross pattern to 22 ft. lbs. (30 Nm).
  11. Refill the axle with the proper quantity of SAE 80W, SAE 80W-90 GL-5 or limited slip gear lubricant. Replace the filler plug and torque to 29 ft. lbs. (39 Nm). Take the vehicle for a short ride and ch