TH350 Leak Weird one here

[RodC]

This same thing happened to me today with my TH350C, parked on a steep hill. I found this article in the NGs.

Has anyone else had this happen, and if so where can you get some kinda seal for the Yoke??

I'm sure the yoke on my driveshaft is not off the same pickup that my TH350C came off of. Well here is the article, a bit long but....


From: john d. robinson (john@coefac.engr.wisc.edu)
Subject: th350 trans leak -- long
Newsgroups: rec.autos.tech
View: Complete Thread (3 articles) | Original Format
Date: 1997/07/14


howdy,
I have a 1976 th350. it is a rebuilt unit with 10,000 miles and
10 months on it. about two months ago, I parked it on a very steep
hill with the front of the truck pointed up the hill. After 15 minutes
or so, I went back to the truck, to find a quantity of trans fluid on
the ground underneath the truck. investigation found that there was a
small amount of oil sprayed on the undercarriage and cab floor around
the end of the trans at the output shaft. Further investigation shows
that fluid is leaking from the yoke, not the seal, on the output
shaft. I removed the shaft, thinking that I would find a crack in the
yoke, to find a 1/16th hole drilled in it at the factory(?).
On pondering this hole, I decided that the yoke shaft would need
a relief for oil that might get trapped between the trans output
shaft, inside the trans, and the yoke output shaft. And so that, when
the truck was at an extreme angle, the trans oil collected in the
tailshaft, and leaked out this hole.
And so, I reassembled the shaft, added fluid, about a pint, and
didn't think about it anymore, nor did I lose any more fluid.
However, I recently installed a new engine (1963 348 , runs
good!) in the truck, and, when removing the engine, discovered that
the rear trans mount was torn. When I replaced it, I accidently tipped
the transmission so that the output shaft was at an extreme angle ,
probably causing any fluid to pool at the back end of the trans. I
then installed the engine and trans.
The next day I noticed a LARGE quantity of trans fluid on the
ground.
As I was still working on the engine, I figured the same problem
happened, and after several days of finishing, the engine ran, and I
installed 3 quarts went into the trans upon assembly and running of
the new engine.
After driving for about 100 miles for the break in trip, (stop and
go, and some hiway also) I parked on my slightly sloped driveway.
After about 2 hours I noticed a small amount of trans fluid dripping
from the tailshaft yoke again.
FINALLY, my question is this. What is happening? is my diagnosis
of fluid collecting in the tailshaft correct? is the trans failing?
Why am I still leaking fluid at the tailshaft? The fluid level is
correct. got any imput?
Thanks,

John Robinson, Mechanician
Mechanical Engineering University of Wisconsin
1513 University Ave.
Madison, Wi. 53706
608-262-3606
FAX 608-265-2316
Current World Land Speed Record Holder
Bonneville Salt Flats
H/GCC 92 cu.in. 1980 Dodge Colt
131.333 MPH set 1995
136.666 MPH set 1996


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Rod Childers
'71 C10 Stepside

[69 longhorn]

Some of the hydros had an o ring seal on the output shaft,the the yolk slipped over. when the seal gets worn ,you have a leak out the hole on the welch plug thats on the back of the yolk. You can remove the tailhousing,& replace the o ring,or weld up the hole(I have done this,with no problems)......69