Analysis of Leakage

Clean up the leaking area enough to identify the exact source.
A plugged axle housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.
Make sure axle lubricant level is 6-14 mm (1/4-9/16 inch) below the bottom of the fill hole.

Axle Vent

Note: If a plugged vent cannot be cleared, install a new one.

A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent. Make sure the vent hose is not kinked. Remove the hose from the vent nipple and clear the hose of any foreign material. While the hose is removed, pass a length of mechanics wire or a small diameter Allen wrench in and out of the vent to clean it. Connect the hose when done.

Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
- Seal was not correctly installed.
- Poor quality seal journal surface.
Any damage to the seal bore (dings, dents, groups, or other imperfections) will distort the seal casing and allow leakage past the outer edge of the axle drive pinion seal.
The axle drive pinion seal can be torn, cut, or gouged if it is not installed carefully. The spring that holds the axle drive pinion seal against the pinion 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 pinion flange may blacken, indicating excessive heat. Marks, nicks, gouges, or rough surface texture on the seal journal of the pinion flange will also cause leaks.
Axle drive pinion seal wear 1.27 mm (0.050 inch) or greater is considered excessive.
A new pinion flange must be installed if any of these conditions exist.
Metal chips or sand trapped at the scaling lip may also cause oil leaks. This can cause a wear groove on the pinion flange and heavy pinion seal wear.
When a seal leak occurs, install a new seal and check the vent and the vent hose to make sure they are clean and free of foreign material.

Axle Shaft Seals
Axle shaft oil seals are susceptible to the same kinds of damage as axle drive pinion seals if incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid culling or tearing it. Axle shaft journal surface must be free of nicks, gouges, and rough surface texture.