Leaky T350 Shaft/Yoke?

This is officially driving me nuts, so hoping you experts can help. Since I swapped the 350 tran in Joyce's 31 pickup for the Summit 350, I've had constant fluid leakage from the tailshaft/yoke. I welded up the seephole in the yoke - slowed it down a bunch, but still leaks.

The original was short tailshaft and the Summit trans in there now is long tailshaft - shortened and re-used the driveshaft. I know the obvious fix might be to simply replace the yoke seal, but before I did that I was wondering if there is an obvious yoke/trans mismatch here that I need to address...? If so, what should I look for make sure the yoke/trans work together to keep the fluid inside? Didn't some combos use an O-ring in the tailshaft...?

Any help would be appreciated - thanks!

 

the yoke with the hole takes A cup. By yoke w/o hole.

 

OK - aside from the seep hole, what the difference in the yokes that makes the one with the hole need the cup/o-ring and the one without the hole not need the cup/o-ring? Different tailshaft seal? Other?

 

if the old yoke has any ruff spots on it it will leak past the seal ,, take ot out and run your hand down it ..if its not smooth as a babys ass change it

 

The one with the hole is supposed to bolt in, hence the hole. That application uses driveshafts with a slip spline in the shaft and the yoke doesn't slip/move. But you need an O ring since the threads will leak. The one without the bolt hole obviously doesn't need the extra seal, since there's no hole to leak out.

I'd get the right yoke and go from there. Over the years have seen some major hokeyness with people sealing those holes, and some major hokeyness with undrilled holes opening up due to casting flaws.

good luck

 

The hole I welded up wasn't a bolt hole - it was a tiny (1/16") hole in the center of the yoke, in the flat spot between the yoke 'ears', aligned with the hole in the end of the tailshaft.

VIC - I'll check again for rough spots, but I didn;t notice any when I had it apart to weld up that hole.

 

Are you yoking?

 

When you weld up the hole,theres A o ring behind the plug that melts.

 

the way i fixed mine was by putting plastic and silicone over the yoke and then poking it in. been that way for 2 years and no leaks. crappy fix but it worked.

 

Some TH-350's had an O-ring on the output shaft which sealed against a portion of the inside of the yoke that was smooth (not splined). Ive been told that the weep hole was added by the factory to release trapped air inside the yoke. The reason was to reduce the hammering effect (due to compression of the air) when the yoke slid into the trans due to suspension travel. The O-ring is there to keep the fluid away from the weep hole.
If you dont have the O-ring, the weep hole is just an annoying leak, unless you park pointed downhill.
I welded up a weep hole and it only slowed down the leak, turns out it was a lousy weld. The only way to be sure is to weld it up, (let it cool) then fill the yoke with trans fluid, or better yet, solvent, and check for leakage.

 

Thanks. If I can't get this to seal up, I'll try to find another yoke that mates with the trans that doesn't use the cup/o-ring.

 

a two wheel drive Chevrolet 350 is a medium shaft, it does have a cup and O ring. They are bad about leaking, so far you know all that. What I have done in the past and it has worked for 30 years so far is to stuff the yoke with a piece soft paper and put in a nice "glob" of silicon sealer, then reinstall the shaft. I know this sounds shade tree but you'd be suprised how many come through this shop that has already been done that way. Try it...its cheep and it works.