GM Firebird 1967-1981 Repair Guide

Rear Axle

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LEVEL CHECK



The oil in the differential should be checked at least every 6,000 miles (7,500 miles for 1975 and later models).

  1. With the car on a level surface, remove the filler plug from the front right side of the differential.
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  3. If the oil begins to trickle out of the hole, there is enough. Otherwise, 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.
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  5. If not, add oil through the hole until the level is at the edge of the hole. Most gear oils come in a plastic squeeze bottle with a nozzle; making additions is simple. You can also use a common kitchen baster. Use only standard GL-5 hypoid-type gear oil SAE 80W or SAE 80W/90.
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On all models equipped with a positraction/limited slip rear axle, GM recommends that you use only the special lubricant which is available at your local Chevrolet parts department.

DRAIN & REFILL



See Figures 1 through 7

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Fig. Fig. 1: If your rear axle is a Positraction unit, it should exhibit a metal ID tag, as shown



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Fig. Fig. 2: Before draining the rear axle unit fluid, make sure the fill plug can be loosened



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Fig. Fig. 3: To drain the rear differential, remove all cover retaining bolts, except for the top one (arrow) ...



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Fig. Fig. 4: ... then loosen the top bolt slightly and pry the cover away from the housing to drain the fluid



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Fig. Fig. 5: Remove the cover (after most of the fluid drains) to allow the residual fluid to drain out of the housing



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Fig. Fig. 6: Cover the gears with a clean rag and remove the old gasket from the housing ...



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Fig. Fig. 7: ... install the cover with a new gasket, then add fluid to the unit through the fill hole

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

  1. Park the car on a level surface and set the parking brake.
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  3. Remove the filler plug.
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  5. Place a large container underneath the rear axle.
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  7. Unscrew the retaining bolts and remove the rear cover. This will allow the lubricant to drain out into the container.
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  9. Install the rear cover using a new gasket and sealant. Tighten the retaining bolts in a crosswise pattern.
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  11. Refill with the proper grade and quantity of lubricant. Replace the filler plug, run the car and check for any leaks.
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