61 GMC Hydramatic yoke

[Surfdaddy]

Is the yoke on my Hdyramatic the same as a TH350? or, would a trans shop have a yoke that I can get to replace the one I have. The trans is still leaking out the tail shaft after a few days of sitting. Saturday when I drove it on the freeway I saw smoke come and go. I looked and is coming from the tailshaft, leaking on the cross member and dripping on the exhaust. The only thing I can think of is the yoke is bad causing the seal to leak. I really need to get that fixed first before I tackle any of the other minor problems I have. All in all the truck is working out ok. No big problems just the endless list of minor things that you get with an old car.

[padresag]

there could be a couple of answers here. 1 the rear seal is gone and requires replacing. 2. there is a rear bushing that is worn and needs replacing and the yoke itself can be worn at the 2 other locations that I mentioned. all 3 of them can be buggered. you will not know until you take it apart
ron

[Surfdaddy]

The thing that stinks is I litterly had the trans rebuilt 4 months and less than 500 miles ago. I had bought a complete master rebuild kit and had a trans shop do it. Perhaps I should go to the trans shop and ask. I know that the seal should be replaced since it leaked and is most likely torn or has a knick in it.

[padresag]

who re and re it. you or them?
this was posted on Jollies site a while back was it not? .if you run a dialoque at one place instead of not liking an answer you may get to the bottom of it. . you will still have to pull that d/s out to have a look at the yoke as you answer will more than likely lie there
ron

[Clyde65]

I got nothing, I thought what I was reading said it was the same as TH400, but I dont know for sure

[Surfdaddy]

I asked the question on Golly’s site and the answers confirmed what I thought may be the problem. Either the rear seal was not put in correctly or the yoke has some sort of scoring that is allowing the seal to leak. I was going to take the drive shaft off and check the yoke but the leak stopped after I was driving the truck every day or so and I truthfully forgot about it until it started again when I parked it for two weeks.
The reason for me asking if the yoke is the same or not is the guy at the tranny shop may not know too much about this trans and may have been trying not to have to do any warranty work. He said I need to put a yoke from a turbo 350 on it and that would solve my leaking problem. Since I don’t trust him and think he’s just trying to make me go away I thought I would ask the question. Is the yoke the same on the Hydra-matic and the TH350. I'm guessing not.

[Surfdaddy]

I just spoke to the owner of Transmatic in Glendale, a real nice but old and frail guy. I bought the master rebuilt kit from him. I asked about the yoke and the seal and what the problem could be. I told him about the leak stopping and then starting again. He let me in on a few things that I thought might be interesting.
First of all I KNOWI WILL HAVE TO remove the drive shaft and inspect the yoke and since I’m there I will replace the rear seal. And I hope that this will solve the problem. While I have the drive shaft out I’ll replace the u-joints since they seem to be worn.
But after saying that, when the trans was installed I looked at the yoke (not too closely) and I didn’t notice anything that jumped out at me.
I was thinking that what would cause the seal to leak and then stop leaking after driving and start again after sitting for a while (days or a week) The guy said that the seal may get a flat spot in it, and loosen up after it jets warmed up. And then when sitting get another flat spot in it. I’m not buying that since unless it was a real old seal to begin with it should keep it’s elasticity. But I did think what if the converter leaked and filled the case up. The seal would not be able to stop fluid from seeping around the yoke and leak out. He thought of this without any input from me at all. He called it converter bleed back and said that it was rare in the Hyda-Matic but very possible. Solving this problem is not very easy but he says he has all the parts to repair it if needed. He also said that he would research and see what it takes to determine if that is the problem or not. Meanwhile I’ll pull the drive shaft check the yoke, replace the seal and replace the u-joints.

[padresag]

your not going to know whether they are the same unless you have them both together to match them up for spline and external measure. I may know where there is a yoke, but would have to check to see if he still had it(62 gmc).
he said that you needed to put a yoke from a 350 on it and that would solve any leaking problems. that tells me that he knew that there was a problem with it and he neglected to tell you at the time. there are things then with the yoke such as a groove where the seal ran and it has worn a groove(can be repaired with a speedi-sleeve, but is really not long term(forever) but can be replaced again. he may have chucked it up and polished it and went to far(undersize) that the seal may not be sealing properly and he didn't want to tell you and hoped that it would disappear.
If I can remember properly the early hydramatics had a fine spline and was a little larger dia than a chev would have been.
there could have also been a plug (like a slightly domed frost plug without a lip) in the ujoint end of the yoke; perhaps missing, maybe fluid coming from there? , but that wouldn't be under any pressure.
remember those trans haven't been used for 50 years and you may have had an old old o/haul kit
he may not have lubed the yoke well enough when he installed it.
if the convertor seal around the flywheel goes(o'ring), it will leak out the bottom of the b/housing area. the frt pump seal wouldn't bleed bad that much into the housing a cause an overfill leak out the back and besides it didn't start leaking untill you drove it again'
you can get a yoke hard chromed and remachined back to std if needed
ron
there is always a solution

[Surfdaddy]

Actually other than the messy surprise and the inconvenience of having to pull things apart again I find these problems very interesting. I think working on this stuff is sometimes challenging and truthfully pretty fun though sometimes a real pain. The guy at TransMatic did say that it was not a typical problem for the converter to bleed back into the case but is has happened before. I’m pretty confident that the problem is pretty minor and will be solved by a seal and a yoke. Tracking down old parts is part of the fun of restoring an old car. I’ll have to look into finding out what the specs are for the diameter of the yoke and see if it’s in tolerance or not. I really hope the rear bushing isn’t bad though it should have been in the master kit. That may be a pain to replace while the trans is on the truck.

[padresag]

By rondavid at 2009-11-22
it looks like it had a coarse spline, so you may get lucky on another'
to change that rear bushing is not great of a problem as you would just pull the speedo gear and remove the rear tailhousing and it is in there
ron

[Surfdaddy]

I’ll look at this weekend if it isn’t raining. It’s hard to complete one simple thing when you have too many projects. I thought I was finished with the VW and I was concentrating on the truck when the motor in the VW went south. So, I’ll have the all the parts for the new motor next week. That leaves me this weekend to fix the truck.

[Str8axle]

Hydro yoke and TH350 yoke aren't even CLOSE to being the same. A course spline 3spd yoke won't work either. Don't bother, I've tried it.
As said above, check your yoke to see if it has a slight groove worn in it where the seal rides. If so, you may be able to get a speedy sleeve to fix your existing yoke. I know they sell them for harmonic balancers, and you may be able to match one up. And also check the center of the yoke for a plug resembling a freeze plug. It will leak if damaged or not there. I'll check the yoke on my Hydro today and post pix later of what I find.

[Surfdaddy]

Doin it tomorrow if it isn't raining. If it's bad then I'll call the guy at TransMatic and see if he has a new yoke and seal. (I'll probably age a seal and teh end cap seal regardless) I know for sure there isn't a plug on the end of the yoke so that may be my problem. I'm going to replace the u-joints at the same time. I have some driveline vibration issues that I think are u-joints.

[Str8axle]

Here's some pix.
The first one is a TH350 yoke on the left and a Hydro on the right.

Second pic shows that they are the same diameter

Third pic is a 3spd on the left and Hydro on the right.

[padresag]

by the way it is not hydro. hydro is electricity. hydra is for hydraulic-hydramatic
ron

[Str8axle]

Well, if you must get technical, it's Hydra-matic for these transmissions. And in my case, it is Hydro due to the fact that my yoke is from my B&M Hydro race trans....

[padresag]

Originally Posted by Str8axle

Well, if you must get technical, it's Hydra-matic for these transmissions. And in my case, it is Hydro due to the fact that my yoke is from my B&M Hydro race trans....

that is basically what I said above. a hydramatic trans is a hydraulic application . how about showing us a picture of their trademark B&M Hydro

ron

[Str8axle]

Here you go...
Hydro built to B&M specs. Chevrolet V8 application. Ultra rare "upside down" starter. Torus vanes cut and furnace brazed. Full manual control. No park provision (parking pawl removed). Hurst Hydro-Gate shifter.

[Rich 5150 69]

Ah.... come on Ray.....I just got myself settled down on this for a while, now I`m all torqued up again with those pics....I have found two `53 units, but still know adapters...LOL

[Str8axle]

He asked....

[Rich 5150 69]

One unit was a olds slant pan, the other a caddy... hav`ent seen it yet tho.

[Str8axle]

Rich, I have a '55 Pontiac unit for ya if you were closer. I think we can make an adaptor. The hard part is the flywheel and torus. Chevys use a small torus and Pontiacs use the large one. I do have a Chevy six cyl flywheel and torus but the center of the flywheel would have to be machined "if possible" to fit a V8 crank.

[padresag]

Originally Posted by Str8axle

Here you go...
Hydro built to B&M specs. Chevrolet V8 application. Ultra rare "upside down" starter. Torus vanes cut and furnace brazed. Full manual control. No park provision (parking pawl removed). Hurst Hydro-Gate shifter.

what you are referring to is a shifter, not the trans and that may be just slang to. perhaps you can drag up a piece of literature that Hurst really called it that.
ron

[Rich 5150 69]

Ray I will keep note of that...this is a back burner project right now, I can easily get distracted with this.....but still want to do this.

[Str8axle]

First pic: embossed on shifter mount

Second pic: tag on side of transmission case

My apologies to Surfdaddy. Didn't mean to hyjack your thread.