GM Full-Size Trucks 1980-1987 Repair Guide

Drive Axle (Rear and/or Front)

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FLUID RECOMMENDATIONS



Front axles use SAE 80W-90, GL-5 Gear Lubricant. Rear axles use SAE 80W-90 gear oil. Positraction or locking axles must use special lubricant available from dealers. If the special fluid is not used, noise, uneven operation, and damage will result. There is also a Positraction additive used to cure noise and slippage. Positraction axles or locking axles have an identifying tag, as well as a warning sticker near the jack or on the rear wheel well.

LEVEL CHECK



See Figures 1, 2 and 3

The fluid level in the front axle should be 1 /2 in. below the filler plug opening. The fluid level in the rear axle should be up to the bottom of the filler plug opening. Lubricant may be added with a suction gun or squeeze bulb.



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Fig. Fig. 1: The rear axle filler plug is located on the rear housing cover for some vehicles

  1. Park on level ground.
  2.  
  3. Remove the filler plug from the differential housing cover.
  4.  
  5. If lubricant trickles out there is enough. If not, carefully insert a finger and check that the level is up to the bottom of the hole. Locking front hubs should be run in the LOCK position for at least 10 miles each month to assure proper lubrication to the front axle.
  6.  



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Fig. Fig. 2: On this vehicles, the rear axle filler plug is located on the side of the housing



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Fig. Fig. 3: The square plug may be removed by a standard ratchet extension

DRAIN AND REFILL



See Figures 4, 5, 6 and 7

  1. Park the vehicle on the level with the axles at normal operating temperature.
  2.  
  3. Place a pan of at least 6 pints capacity under the differential housing.
  4.  
  5. Remove the filler plug.
  6.  
  7. If you have a drain plug, remove it. If not, unbolt and remove the differential cover.
  8.  
  9. Replace the drain plug, or differential cover. Use a new gasket if the differential cover has been removed.
  10.  



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Fig. Fig. 4: On rear axle housing not equipped with a drain plug, the rear cover must be removed to drain the fluid



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Fig. Fig. 5: Once all retaining bolts are removed, pry the bottom of the cover back to break the gasket seal



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Fig. Fig. 6: Gear oil is added through the filler plug bore, using a hand pump



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Fig. Fig. 7: Once fluid begins to trickle oil, install the plug back into the bore

 
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