FLUID LEVEL CHECK
See Figures 1, 2 and 3
The fluid level in the rear axle should be checked at each oil change. Like the manual transmission on the Mustang, the rear axle does not have a dipstick to check its fluid level. Instead, a filler plug is located in the side of the housing (or in the side of the cover), just barely above the level to which fluid should fill the housing.
- Make sure the transmission is in P (A/T) or in gear (M/T), then FIRMLY set the parking brake and block the drive wheels.
- Check under the vehicle to see if there is sufficient clearance for you to access the filler plug on the side of the differential housing. If not, you will have to raise and support the vehicle using jackstands at four points to make sure it is completely level. Failure to support the vehicle level will prevent you from properly checking or filling the rear axle fluid.
- Thoroughly clean the area surrounding the fill plug. This will prevent any dirt from entering the housing and contaminating the gear oil.
- Remove the fill plug and make sure that the gear oil is up to the bottom of the fill hole. If a slight amount of lubricant does not drip out of the hole when the plug is removed, additional lubricant should be added. Use hypoid gear lubricant SAE 80 or 90.
If the differential is a Traction-Lok limited-slip unit, be sure to use 4 oz. of Ford Friction Modifier C8AZ-19B546-A or equivalent special limited-slip additive with the lubricant.
- Once you are finished, install the fill plug, then (if raised) remove the jackstands and lower the vehicle.
DRAIN & REFILL
See Figures 4 through 11
Drain and refill the rear axle housing every 100,000 miles (160,000 km) or any time the vehicle is driven in high water (up to the axle). Although some fluid can be removed using a suction gun, the best method is to remove the rear cover to ensure that all of any present contaminants are removed. As with any fluid change, the oil should be at normal operating temperature to ensure the best flow/removal of fluid and contaminants.
- Drive the vehicle until the lubricant reaches normal operating temperature.
- If necessary for access, raise and support the vehicle safely using jackstands, but be sure that the vehicle is level so you can properly refill the axle when you are finished.
- Use a wire brush to clean the area around the differential. This will help prevent dirt from contaminating the differential housing while the cover is removed.
- Position a drain pan under the rear axle.
- Loosen and remove all but one or two of the rear cover upper or side retaining bolts. The remaining bolt(s) should then be loosened to within a few turns of complete removal. Use a small prytool to carefully break the gasket seal at the base of the cover and allow the lubricant to drain. Be VERY careful not to force or damage the cover and gasket mating surface.
- Once most of the fluid has drained, remove the final retaining bolt(s) and separate the cover from the housing.
- Carefully clean the gasket mating surfaces of the cover and axle housing of any remaining gasket or sealer. A putty knife is a good tool to use for this. You may want to cover the differential gears using a rag or piece of plastic to prevent contaminating them with dirt or pieces of the old gasket.
- Install the rear cover using a new gasket and sealant. Tighten the retaining bolts using a crisscross pattern.
Make sure the vehicle is level before attempting to add fluid to the rear axle, otherwise an incorrect fluid level will result.
- Refill the rear axle housing using the proper grade and quantity of lubricant, then install the filler plug. Lower the vehicle, if applicable, then operate the vehicle and check for any leaks.