I've seen people discuss the idea of tranny fluid leaking into the xfer case.
I just had an SYE installed by a local shop, and this is the diagnosis they
gave me after I got it home and it started leaking from the bottom of the
case and tail shaft. I say impossible, I've never in my life seen or heard of
fluid leaking INTO a seal. But, since that was their answer, and the fact that
they were not going to charge me to fix it, (Because they could have damaged the
seal when installing the new shaft... they did not remove the xfer case, they
split it while still in the jeep.) I let them pull it and replace both seals.
Guess what? still leaks from the bottom of the case and tail shaft. But I'm trying
to curb my rant hehe. I called my local jeep dealer and ask if the tranny to xfer
case fluid thing was possible and he said in his 20 years there as a service advisor
he had never heard of such.... even tho the mech that worked on mine said, "Oh, yeah,
we see it all the time." I've read a lot on your forum here and respect you guys opinion.
So, anyone here think this is possible? Or bunk?

 

I have a '91 with a NP 231 and my book says to run ATF in it. Same with my wrecked '92 with a NP 242. So, while the TC may be leaking, I doubt that it's leaking from the tranny into the TC.

 

Yeah, they said it was over full from the tranny leaking into it...... It might have been a little over full from when I filled it up when it was half empty from the leak. I swear I told them that too. Thanks for the reply.

 

if they both take atf then how do you know where that particular drop of atf came from?? lol

kinda like saying that water in the pool came from a leaking pool pump lol

 

hehe like a pool pump leaking into the neighbors pool pump

 

It is not unlike a differential, you fill it level with the fill plug & your done, can't over fill unless you remove the indicator light sending unit & dump it in there. Is it leaking between the halves? Did they crack the case splitting it?

 

There's an adaptor between your AW4 and your NP 231. The adaptor incorporates a seal around the output shaft of the tranny that prevents ATF from escaping the tranny. The TC has a seal around the input shaft of the TC that prevents ATF from escaping the TC. Both seals are exposed to the middle of the adaptor. The bottom of the adaptor has a weep hole in its bottom that will allow ATF leaking from either the tranny or TC seal to run out of the adaptor. It is highly unlikely that ATF from the tranny blowing past its seal in the adaptor would enter the TC past its seal on its input shaft.

ATF leaking from a TC may be caused by over filling the TC or its vent being plugged. The vent hose from the TC goes to a breather valve located next to the tranny dipstick tube. The breather valve is a strange device and and plugs up easily. If you can find it, remove it and try to clean it out with TB cleaner, then blow through it in both directions to see if it is clear. I tried this and the valve was so contaminated I couldn't get it clean, so I replaced it with a front differential breather valve.