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Hi,
Noticed a trans leak coming from the slip yoke on my ‘70 Supreme TH350. I am not certain if it’s the yoke type with a weep hole but it appears to be as the tail shaft housing is dry and the bushing/housing seal is new. I don’t want to seal up the hole as it does serve a purpose and would like to address the issue. Is this an o-ring on the shaft that causes this to leak? Id like to try and source parts that I need before I dig into it so I’m not stuck in the middle of the job. Also for this type of u-joint, is this the c-clip style with the clips on the inside edge of the needle bearing caps?
The best fix is to seal it up. The yoke is most likely worn enough by now that you don't need the vent anymore. Try to get a wheel cylinder cup the correct diameter, a little loose fit, coat the flat side with RTV and push it down into the yoke. You should see a little RTV come out of the hole. Of course, clean the inside and outside first with brake cleaner. I have fixed many this way when I managed and later owned a transmission shop..
Some Th350 have a sleeve pressed on the output shaft, inside the extension housing, with a O-ring that seals around the outside diameter of the yoke. It’s usually found on truck transmissions, maybe the cars used them also.
Transmission yokes with the vent hole will use the sleeve with the o-ring. Yokes without the vent hole will have one internal spline missing, the missing spline groove serves as a vent. As the yoke moves over the output shaft the space in the yoke needs to breath.
If the yoke is in good condition, the bushing isn’t sloppy, and the seal is good, you need to remove the extension housing to see what’s inside. The o-ring is included with every overhaul gasket kit, most of the time it’s get thrown away because it’s usually not needed. Chances are a local transmission shop will have one. If not, pm me. I have a bunch.
As someone mentioned, it’s not uncommon to find a transmission that leaks after sitting awhile. If it only leaks after extended time parked, I wouldn’t worry about it. Chances are, you will fix the extension housing leak, only to find the fluid will find a new place to leak after sitting.
Does anyone have the Part # for this O-Ring for the TH400 ? I am in same boat and I'm betting my O-Ring is toast. Seems like an easy fix, just need to know the part # so I can order from Summit.
Does anyone have the Part # for this O-Ring for the TH400 ? I am in same boat and I'm betting my O-Ring is toast. Seems like an easy fix, just need to know the part # so I can order from Summit.
Had the same annoying weep hole leak after replacing ALL other trans gaskets. I replaced the yoke on my 350 TH with one that doesn't have a hole in the yoke. I researched this on other forums as well. Others welded the hole with JB Weld or spot welded.
Would putting a short screw with an o-ring or gasket under the head into the hole work? It's easily reversible if it causes an issue.
Or as stated drive it more often.
March 2nd, 2021, 10:05 AM
