[Rich-Tripower]

The pinion seal on the GTO is leaking again. Or maybe I should say still. It doesn't leak when sitting but during a drive it leaks enough to get the axle housing and gas tank greasy. It drips lube after being parked after a drive, but if the grease is cleaned off it doesn't leak any more until the next drive.

The pinion seal itself has been replaced at least three times. The last time we installed a brand new yoke (that was hard to find) and a new seal to fit the yoke. It was dry for a while and started leaking again. The pinion threads were properly sealed, the case where the seal installs is sound, no cracks or gouges. I'm at wit's end as to why this thing is leaking so much with everything new. Also, when the axle/transmission shop who did the work last (new seal, yoke, etc.) worked on it they had it on the lift with it running and in gear and no wobbles or out of balance situations were observed (one bent wheel was discovered and that was replaced but not related). During the restoration the driveshaft was rebuilt and rebalanced and the shop that did the axle work verified the pinion is not wobbling. No weird drivetrain noises or vibrations are felt during a drive.

The only thing I can think of is that the vent on the top of the axle is plugged. I think I may have checked this before but worth checking again. Anyone know a way to verify the vent is open to the internals of the differential? Any other ideas what the issue could be with the seal? This last time around everything was installed by a very experienced shop so I assume everything was installed properly. Herb, the guy that did the work is a real (old) car guy, he probably knows the old stuff better than the new stuff and really, a pinion seal is a pretty basic component. He went above and beyond to find a new pinion yoke for me.