Can a transmission leak through the yoke and U-joints?

[davepl]

I have what appears to be a "two drip a day" transmission leak. It is coming out of the U-joint at the back of the trans.

The trans and the trans seal are dry. I thought perhaps it was just grease I packed into it during assembly coming out (red grease, red trans fluid, hard to say). But it's been doing it for a couple of weeks now and I don't think there's enough supply in a U-joint cap to account for it.

I switched over to the big (1330 or 1350?) yoke, as it is a 200-4R and wanted to retain my driveshaft.

If not through the yoke, is there anywhere else I can check?

[geezer#99]

Some yokes have a vent or weep hole in them. Dead centre.

[bonnieclyde100]

they will tend to leak if the truck sits for a long amount of time. trans fluid slowly works its way out of the converter and then it will leak through the yoke. my truck will do it if it sits for more than a couple of weeks.

[Bigdav160]

What geezer said. Truck yokes have a weep hole. The transmission would have a seal sleeve inside to keep fluid from wicking down the splines and leaking out the hole.

I'm pretty sure their were never any seal/sleeves for the 200-4r so go ahead and weld up the hole in the yoke.

[old Chevy guy]

hhmmm, I'm no expert but I think that hole is there so air can vent in and out as the yoke travels in and out as the truck goes up and down. Id research it a bit deeper before I'd weld up the hole. Better to weld it later than try and drill it out again.

[mechanicalman]

Originally Posted by davepl

I have what appears to be a "two drip a day" transmission leak. It is coming out of the U-joint at the back of the trans.

The trans and the trans seal are dry. I thought perhaps it was just grease I packed into it during assembly coming out (red grease, red trans fluid, hard to say). But it's been doing it for a couple of weeks now and I don't think there's enough supply in a U-joint cap to account for it.

I switched over to the big (1330 or 1350?) yoke, as it is a 200-4R and wanted to retain my driveshaft.

If not through the yoke, is there anywhere else I can check?

Yes, it can leak through the yoke even if there is no weep hole. Due to machining of the internal splines in the yoke, it has to be open on both ends during the process. There is a plug in the rear similar to a freeze plug that can sometimes leak on the outer edges. I have fixed them before with JB weld, only to have them start leaking again later necessitating a replacement yoke, and coincidently those were on 200R4s in Cadillacs back in the 80s.

I'd clean it as good as possible and silver solder it like a water pipe. Never tried that before, I just now made it up so can't say I've done it but I have silver soldered many, many high pressure diesel injection lines (up to 2800 lbs psi) and that stuff is quite dependable just make sure you flux it good first.

You might get it mig or tig welded as well. Otherwise, replace the yoke.

[mechanicalman]

Originally Posted by old Chevy guy

hhmmm, I'm no expert but I think that hole is there so air can vent in and out as the yoke travels in and out as the truck goes up and down. Id research it a bit deeper before I'd weld up the hole. Better to weld it later than try and drill it out again.

On the ones with the hole, yes, it's there to vent back in the day when oil drips were expected.

If the yoke is out of the donor vehicle's 200R4, it will not have a weep hole, it will have one spine missing to perform that vent function.

Dave, make sure you have an open area in the splines on the yoke or the shaft, I think it's on the yoke but can't remember 100%.

[no1udknow]

I think I would try something simple first like a rubber plug or something that way if it blows out of there quickly, you know it needs to be vented.

Im not a transmission guru, Is the transmission vented elsewhere, perhaps that ven is restricted and pushing some fluid into the splines.

[brad_man_72]

We usually used plastic weld to seal the plug and the hole too. If you haven't had the driveshaft ballanced a vibration can cause a leak.

[mechanicalman]

Originally Posted by no1udknow

I think I would try something simple first like a rubber plug or something that way if it blows out of there quickly, you know it needs to be vented.

Im not a transmission guru, Is the transmission vented elsewhere, perhaps that ven is restricted and pushing some fluid into the splines.

That's good critical thinking no1udknow.

Maybe not a transmission guru, but

a pretty smart feller!

not a good speller!
LOL

[no1udknow]

Originally Posted by mechanicalman

That's good critical thinking no1udknow.

Maybe not a transmission guru, but

a pretty smart feller!

not a good speller!
LOL

I blame most of my spelling errors on the fact that my smartphone has a very small keyboard, and I have very large thumbs.