FLUID LEVEL CHECK
See Figure 1
The oil in the front and/or rear differential should be checked at least every 7500 miles (12,000 km) and replaced every 25,000-30,000 miles (40,000-48,000 km). If driven in deep water it should be replaced immediately.
- With the truck parked on a level surface, remove the filler plug from the back of the differential.
The plug on the bottom is the drain plug.
- 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 to see if the oil is up to the bottom edge of the filler hole.
- 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 simple. You can also use a common kitchen baster. Use standard GL-5 hypoid type gear oil; SAE 90 or SAE 80 if you live in a particularly cold area.
- Replace the filler plug and drive the truck for a while. Stop the truck and check for leaks.
DRAIN AND REFILL
See Figures 2, 3, 4, 5, 6 and 7
The gear oil in the front or rear axle should be changed at least every 25,000-30,000 miles (40,000-48,000 km); immediately if driven in deep water.
To drain and fill the rear axle, proceed as follows:
- Park the vehicle on a level surface. Set the parking brake.
- Remove the filler (upper) plug. Place a container which is large enough to catch all of the differential oil, under the drain plug.
- Remove the drain (lower) plug and gasket, if so equipped. Allow all of the oil to drain into the container.
- Install the drain plug. Tighten it so that it will not leak, but do not overtighten.
Its usually a good idea to replace the drain plug gasket at this time.
- Refill with the proper grade and viscosity of axle lubricant (see "Recommended Lubricants" chart). Be sure that the level reaches the bottom of the filler plug. DO NOT overfill.
- Install the filler plug and check for leakage.