Pinion Seal Leaks after 2 years and 30,000 miles???

67coupe

Founding Member
Apr 5, 2002
658
402
93
Huntsville, AL
2 years and 30k ago, I installed a set of 3.73's. Hasn't leaked a drop, until now (inspected often, especially the first 6 months after install). I'm positive it's not the cover leaking.

I used the 8.8 rebuild kit from summit. All new bearings, new crush sleeve, new seal, new pinion nut. Tighten pinion nut until drag was in range for new bearings (used a beam style lb-in torque wrench).

What could cause this:

1) Cheap seal
2) Pinion bearings loosing preload (it has developed a clunk recently)
3) Bad luck....

Except for the new clunk and a very slight whine on decel, diff has been very quite. I'm using MM LCA's with spherical bearings at each end, which increase noise transmission. Pattern looked good. Backlash was 0.007" (I think).

I'll double check everything once torn apart. Just want to hear some ideas before I tear it down.
 
Just read something concerning pinion seal leaks. On high mileage cars, a groove can develop in the pinion flange, causing a leak no matter the age/condition of the seal. I had a similar experience with my driveshaft. Leak was fixed with an aluminum driveshaft. The car does have 170k, so this might be it.

Any thoughts/experiences?