My '82 Silverado 350TH automatic transmission has a leak when it is parked with engine NOT running. It is not leaking from the seal that is new but the fluid leaks out from the center of the driveshaft yolk. It does not leak when the engine is running or if parked on a downhill grade. Is there some kind of o-ring seal in the tailshaft of the transmission or in the driveshaft yolk that is supposed to stop this from happening?The front u-joint wore out and that is when I noticed the leak. I replaced the u-joint but can't get the leaking part figured out. All help would be greatly appreciated.

 

Removed the tailshaft housing and found no metal sleeve with o-ring, so I took one out of another tranny I had sitting around, put a new o-ring in it, and installed it on the tailshaft. That stopped the leak from the center of the slip yolk on the driveshaft. I do still have a small leak from a broken speedometer cable housing. It has to be ordered in through Autozone. That should stop all my leaks from this transmission, fingers crossed!