Leaking

Most rear axle leakage conditions can be corrected without a teardown. However, it is important to clean the leaking area enough to identify the exact source.

A plugged or seized rear axle housing vent will cause excessive flange yoke seal lip wear due to internal pressure buildup. When a leak occurs, check vent and vent tube for debris. Clean or replace as required.

Check axle lubricant level. Make sure the axle lubricant level is 12.7 mm (0.50 inch) to 14.3 mm (0.56 inch) below bottom of fill plug hole.

FLANGE YOKE SEAL
When the rear axle drive pinion seal leaks, it may be that it was not installed properly, or because of rough texture or damage on the seal journal surface.

Any damage to the seal bore (dings, dents, gouges or other imperfections) will distort the seal casing and allow leakage past the outer edge of the rear axle drive pinion seal.

The rear axle drive pinion seal can be torn, cut or gouged if it is not installed carefully with the correct service tool. The spring that holds the rear axle drive pinion seal against the rear axle universal joint flange may be knocked out and allow leakage past the lip.

The rubber lips can occasionally become hard (like plastic), with cracks at the oil lip contact point. The contact point on the rear axle universal joint flange is usually black, indicating excessive heat. Marks, nicks, gouges or rough surface texture on the seal journal of the rear axle universal joint flange will also cause leaks. Excessive seal lip wear will be noted. The rear axle universal joint flange should be replaced if any of these conditions exist.

Metal chips or sand trapped at the sealing lip may also cause oil leaks. This can cause a wear groove on the rear axle universal joint flange and heavy seal lip wear.





If the rear axle housing vent is plugged with dirt and debris, the rear axle housing will be pressurized and may result in excessive seal wear and seal leakage.

DRIVE PINION NUT

CAUTION: Removing the pinion nut disturbs pinion bearing preload.

NOTE: Be sure to follow the correct procedure for setting the bearing preload when the nut is installed.

On some high-mileage units, oil may leak past the threads of the pinion nut. Correct the condition by removing the nut and applying Pipe Sealant With Teflon D8AZ-19554-A or equivalent meeting Ford specifications WSK-M2G350-A2 and ESR-M18P7-A on the threads and nut face.

AXLE SHAFT SEALS
Inner wheel bearing oil seals are susceptible to the same kinds of damage as rear axle drive pinion seals if improperly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. Axle shaft journal surface must be free of nicks, gouges and rough surface texture.

Occasionally, the spiral machining lead on the axle shaft seal journal can cause an oil pumping action past the seal. If an inner wheel bearing oil seal leaks after it is replaced, especially on the passenger side, the spiral machining lead may be the problem. If this occurs, replace the suspect axle shaft.

CASTING POROSITY (HOLES IN CASTING)
Rear axle lubricant may leak through small pockets in the metal of the axle housing casting. These pockets (casting leakage) are caused by gas bubbles in the casting process, known technically as a porous condition or porosity.

Because there is a concern of changing the axle's NVH characteristics if disassembled to replace the differential case, service is preferable. There are two recommended types of service.
1. Peen in a small amount of body lead. Seal the pocket with Devcon Aluminum Liquid F2 or equivalent meeting Ford manufacturing standard M3D35-A(E).
2. In larger pockets, drill a shallow hole and tap it for a small setscrew. Install the setscrew and seal it over with epoxy sealer C7AZ-19554-A or equivalent meeting Ford specification M3D35-A(E).

WELD LEAKS





Most minor weld leaks can be corrected with Devcon Aluminum Liquid F2 or equivalent meeting Ford Manufacturing Standard M3D35-A(E). This includes the puddle or fill welds that join the axle shaft tube to the rear axle housing on integral axles. They sometimes leak and can be sealed easily. If a weld is broken, the rear axle housing must be replaced. The alignment is too critical for field service.

AXLE VENT
Lubricant leaking through the rear axle housing vent may be caused by a clogged or sticking axle vent cap. If this is the case, the rear axle housing vent hose should be replaced, using Stud and Bearing Mount EOAZ-19554-BA or equivalent meeting Ford specification WSK-M2G349-A1, on threads to ensure retention.