leaky tranny seal

[1991tc]

I have a 91 town car. When I first got the car, I did the ujoints and other such maintence. I replaced the seal where the driveshaft goes into the tranny because it was shot and leaking. Now the new seal is leaking, but the seal itself is fine? Am I supposed to silicone the sucker in or something? Any advice is much appreciated.

Thanks,
Shane

[Steven]

First the obvious (from the manual):
Analysis of Leakage (rear end, some of this applies to the other end as well)

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. Adjust as required to 12.7-14.3 mm (0.50-0.56 inch) just 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 (4851) 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 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 seal lip wear.


Then the less obvious:
Based on your first post, I'd say your trans has some internal wear especially in the area of the output shaft bushings. Did you ever get it feeling smooth? You mentioned it was feeling rough, did that mean some vibration or noise as well? Inside the output shaft (extension) housing near the end of the output shaft theres a bushing, if it's worn excessivly the output shaft and therefore the driveshaft slip-yoke that goes into the trans will be able to elongate the rear seal during operation causing a leak. The rear seal would still look normal on inspection. Do you notice any up/down play when you apply force to the slip-yoke inserted in the extension housing?
Also there are 3 or 4 (depending on the design ) output shaft seals inside the extension housing before the hub that could be shot as well. If all this applies, the whole extension housing would need rebuilding. Several "special tools" are recommended but it seems fairly simple.
Possible causes of premature bushing wear could be bad engine/trans mounts, unbalanced driveshaft, improper driveshaft installation.

[ November 13, 2002: Message edited by: Steven ]