Transmission rebuild installed now small leak

[teamssc]

We just finished a TH350 rebuild and got it and the NP203 transfer case installed. Now we have some fluid, a leak, showing up around the support where the tranny and transfer case meet up. We had a rough time aligning the transfer case and it took a lot of effort pushing it on. The leak is on the tranny side and is more like seepage, not a fast leak at all. A friend said it might take a little while for everything to seat and seal because tranmission fluid expands the gaskets. We only drove it about 2 miles after the install because I'm putting a new muffler back on.

So, do we have a problem?

 

[teamssc]

No ideas?

 

[foamypirate]

If you shoot HotRodPC a PM, he should be able to help out. He's our resident transmission guru.

 

[HotRodPC]

Are you sure you didn't damage the seal at the input of the Tcase? I'm trying to remember now what goes between the Tcase adapter and Th350. Is it an O ring or a gasket? I'm thinking and O ring for some reason. What did you use? If you didn't use a big O ring, that might be the issue. Models marry in various ways with different type adapters. I suggest just making sure you done the right thing the marrying the Tcase and Trans, but no, it doesn't sound like anything critical as long as it's all working good. Worse case scenario you might have pull the Tcase. You could also leave it for a few hundred miles and see if the seepage stops. Normally you won't hurt a Th350 to bad if it gets low on fluid. When it get's to low it just won't pick up fluid and then it won't move, so then you know to add fluid. Trans might run a little warmer than normal with low fluid too, but nothing catastrophic will happen with low fluid.

 

[teamssc]

I appreciate the feedback.

Actually it's an O ring on the transmission to adapter side and a gasket on the transfer case side. I didn't realize there was a gasket so I didn't have one and we pushed through the install because we both weren't going to have a Saturday to work on it for at least another month. My thinking was that there was no fluid actually living in the space between the two units and the seal & gasket were more to keep dirt out. I based that on thinking that the cone on a 2wd unit didn't have fluid in there (probably wrong). I've just looked at the spare case and support I have and it's pretty obvious that fluid does flow between the 2 units. That's my mistake, we got in a hurry after 8 hours and should have thought about the needed gasket.

Because it is pretty tough to take apart I might use Permatex around the outside and I think I'll have a good seal. I think I can get the surface clean with brake cleaner. Long term if that doesn't provide a good seal I can separate the units and seal it better. I guess I could deal with some slop and loosen the bolts that hold on the transfer case enough to separate it and get Permatex in joint.

Based on your suggestion I don't think I'll loose much fluid.

Thoughts?

 

[HotRodPC]

I appreciate the feedback.

Actually it's an O ring on the transmission to adapter side and a gasket on the transfer case side. I didn't realize there was a gasket so I didn't have one and we pushed through the install because we both weren't going to have a Saturday to work on it for at least another month. My thinking was that there was no fluid actually living in the space between the two units and the seal & gasket were more to keep dirt out. I based that on thinking that the cone on a 2wd unit didn't have fluid in there (probably wrong). I've just looked at the spare case and support I have and it's pretty obvious that fluid does flow between the 2 units. That's my mistake, we got in a hurry after 8 hours and should have thought about the needed gasket.

Because it is pretty tough to take apart I might use Permatex around the outside and I think I'll have a good seal. I think I can get the surface clean with brake cleaner. Long term if that doesn't provide a good seal I can separate the units and seal it better. I guess I could deal with some slop and loosen the bolts that hold on the transfer case enough to separate it and get Permatex in joint.

Based on your suggestion I don't think I'll loose much fluid.

Thoughts?

Yes, a little trans fluid is able to get to the adapter thru the rear bushing of the trans output shaft I do believe. Not alot since it's not under pressure, but nonetheless, some will get in there which should keep the splines lubed.
IIRC, the O rings is all that's required. I'd try the silicone on the outside just for wishful thinking like you said, and if it doesn't do it, them maybe have to seperate them just enough to get silicone at the mating surfaces then bolt them back together up tight.