Here we go again, another tough one... i noticed the differential fluid leaking from the pig on my 10-bolt. i thought it was the pinion seal so i cleaned it up real good and watched it dripping out. good news, its not leaking from the pinion seal. bad news, it is leaking from behind the nut/washer that holds the pinion yoke onto the spline !!! i'm 100% sure that is where its leaking because i removed the nut and washer and can see it dripping out from the splined shaft interface. i think i have that same issue on the harmonic balancer but thats for another day. how am i going to fix the pinion leak ?!?!? what if i buy a new washer and make sure it is clean there, and then crank it down really tight, will it seal ? or should i add some sealant there ? please help, these leaks are driving me crazy !!

Use sealant.

That sucks. Your now messing with the crush sleave and pre-load settings. I have never heard of a leak between the splines before. As Tohcan said you could coat the splines with sealant and try putting it back together. You might get lucky and get the nut tight enough to stay on and not crush the crush sleave any further.

If it were me and it has been before. I would pull the rear end and take it to your local rear end specialist and have a new seal and crush sleave put in. You have to know your limitations and rear end work is mine. Not that expensive and gives peace of mind.

Also check your breather tube. If it is pluged up it will build pressure and force oil out.

If it's the crush sleeve leaking, I hate to say it but sealant isn't going to stop the leak. Replacing that crush sleeve is the ONLY way to stop that leak...

If your leaking gearoil out the pinion it will not be the crush sleeve causing the problem. more than likely you have some wear on the bearing or the race. The crush sleeve is for helping with the pinion depth. If the seal is leaking it will more than likely be caused from the same problem. Seals go out from old age (drying out) tear, or the bearing having to much play. Like mentioned above check the vent to make sure that it is not plugged. Is it possible that it got over filled?

thanks for all the replies.. last year i noticed the pig leaking and thought it was the yoke seal so i installed a new one (marked the pinion nut location and removed it, pulled the yoke and installed a new seal). then i noticed it was still leaking, but upon closer inspection this time, noticed around the seal it was clean and dry. only when i looked around the pinion nut is where i saw the fluid dripping. so i've marked the pinion nut again, removed it and the yoke, cleaned the splines real good, and gooped the splines with RTV and reinstalled. so far it looks dry. i will also check the breather to make sure its clear. as far as i know it wasn't overfilled, i fill the plug hole until fluid just starts to drip out, then reinstall the plug. i also have this issue with the harmonic balancer on the engine (leaks in the keyway groove out to the front of the balancer.. i guess i just have bad luck with those interfaces (or they've been sitting so long (20 years) they've accumulated rust which prohibits a good metal to metal seal).. anyways, i'm hoping the goop is the fix...

Oil will leak through the splines if they are not sealed and come out around the nut. I bet you fixed it.

well , the ole bird has spoken loud and clear i reckon.. i gooped up the splines, new seal and spedi sleeve on the pinion shaft (rtv'd). still leaks !! i'm no master mechanic, but [censored], did all i could.. so its time to replace that original one-wheel-peel rearend with a posi unit. hate to do it, but its time. next stop, parts wanted.. anybody got a posi for a 69' bird for reasonable cost ?

do you see anything funny with this photo. after looking again, its not leaking from the diff, it appears the leak is actually from the brakeline T. big relief !!

That's good news. I surprised you didn't notice a loss of braking first as air might have been drawn in.