tgilligan

Found a trans fluid leak coming from the yoke and after reviewing several forum posts about the issue, how do I determine if my application involves just the transfer case seal or the o-ring that is referenced? Do all the TH350's have the o-ring and is it accessible from once the yoke and driveshaft are removed or do I have to remove the tailshaft as well?

Also, looking to see what the part is called as I have found the transfer case seal available at most stores but I can't find a specific application of the o-ring listed, other than a pack of general/universal o-rings.

svnt442

Transfer case? If you are talking about a Cutlass then you don't have a transfer case as that is only for four wheel drive applications.
The tail shaft housing is bolted to the rear of the main case by 4 bolts and is easily removable, but they don't normally leak at that junction point. Most likely the output shaft seal is leaking and needs to be replaced and that can be done with just removing the driveshaft.

oldsconv

I am not sure the size of that o ring, but a tranny shop could get one easily, or check Fatsco transmission supply in NJ. My chevelle Turbo 400 tranny, which was swapped out at one time and was not the original, had the groove cut for an o ring. You need to take the tail shaft off to get to it, at least on the 400. All that being said, I think the o ring was only used on certain applications. Mine leaked and since the yoke had a vent hole, I had read somewhere, instead of messing with that o ring, just to find a non vented yoke (I.e. No hole in center), or take yoke off and silicone the hole shut from inside. Tranny is vented from top anyway. Put a new output shaft seal on though, while you have it out.

olds 307 and 403

As said no transfer case seal on your cutlass. I just did the rear output shaft seal on my TH350. I bought the kit with tail shaft bushing as well, can leak even with a new seal, if it is worn. The O ring at the end where it attaches to the transmission rarely leaks. I just put a bead of Ultra Black or the Right Stuff on top of the O ring and bolt it back together.