Drive Axle - 7 5/8", 8 1/2", 8 5/8" & 9 1/2" Ring Gears: Lubrication

For all models except C and K series with standard differential, fill differential with appropriate amount of 80W or 80W-90 GL-5 gear lubricant. On models with limited-slip or locking differential, DO NOT add friction modifier.

Some C and K series rear standard differentials require the use of a synthetic gear lubricant. Differentials using synthetic gear oil come from factory equipped with a tag indicating the use of GM P/N 12378261 SAE 75W-90 Synthetic gear lubricant only. Otherwise use 80W or 80W-90 GL-5 gear lubricant. If tag does not exist and there is doubt as to which differential is used in vehicle. VIN must be used through dealership to determine differential usage. See LUBRICATION CAPACITY SPECIFICATIONS  table.