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Leak Where Transmission Meets Transfer Case v2.0

2K views 17 replies 8 participants last post by  ZJeepMI 
#1 ·
Well guys, i'm back, with more problems (well actually the same one). You may remember this thread from a while back:

http://www.jeepforum.com/forum/f13/leak-where-transmission-meets-transfer-case-976549/

The leak mentioned in that thread is still going on, and has not been fixed yet. I suppose I will just take it from the top.

3-4 months ago I killed my NP249 t-case, came grinding to a stop, only ran in 4 low. So I though, the only logical solution is to swap the t-case for an np242 t-case, and just swap the input shafts.

So, I did that I took my 249 out, pulled out the input shaft, and had it swapped into the NP242 at a shop. I put the 242 in myself, and didn't do the seals at that time. I took it for a test drive, and found that I had a really bad leak. So, thats when I posted that thread. I pulled the t-case out after that, and did the seals, once I put it back together it still leaked, just as bad as before.

So, I said screw it, and took it to a transmission shop, they told me that my motor mounts were bad, shaking the trans, causing the seal to break. Sounds reasonable, right? So, they did the motor mounts, and seals again. Still leaks.

That brings us up to last week, they took the t-case out again, did the seals a third time, split the case, and resealed basically everything. It still leaks, just as bad.

We did find out that the leak is not coming from the t-case, it is coming from the transmission. So their theory is that the input shaft is too short and not reaching the transmission seal. Keep in mind that the input shaft in the np242 is the one that came from my old np249. They told me that those were just not compatible for some reason. I have no idea.

I'm sure that was terribly confusing but, I really seriously need some help, advice, ideas, anything with this thing. I am so burned out with this jeep, I'm about to just buy a 249, throw it in, and sell it.

So, any other ideas on what might be causing this leak, or how I could fix it without putting in another 249?
 
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#4 ·
Nope, I know for sure that I got it right when I did it, but I can't see a professional trans shop screwing that up twice.
I don't buy the bit about the input shaft not being long enough, especially since it is the same one that came from your 249. If the fluid is coming from the transmission then it is a problem with the transmission. Is the output shaft from the transmission in good shape? Did it get nicked or scratched when you pulled the transfer case out?
Yup, it definitely sounded pretty sketchy to me too. The output shaft looks good too, it didn't leak at all before the swap. So their idea would make sense, but I don't understand why nobody else has had this problem then. They said they changed some bearings around 94-95, and that is the issue, but I still don't buy it yet.
 
#3 ·
I don't buy the bit about the input shaft not being long enough, especially since it is the same one that came from your 249. If the fluid is coming from the transmission then it is a problem with the transmission. Is the output shaft from the transmission in good shape? Did it get nicked or scratched when you pulled the transfer case out?
 
#5 ·
bump, anybody?
 
#6 ·
The three times the seals in the transfer case have been replaced, did the output shaft seal on the transmission get replaced too?
 
#7 ·
My thoughts exactly

The 249 is almost 100lbs , you can easliy mess the trans seal up when removing it . The 242 is easier to handle at approx 65lbs , but even then , you must be careful when sliding the shaft into the transmission .

I'd recomend replacing the trans seal every time it's exposed
 
#8 ·
Was there sealer between the mating surfaces of the tranny and t-case? I've had a few ZJs now and have found that some have fluid in the adapter and some don't.

Some V8 trannys have a small bleed hole under the output shaft. I you have this then you need sealer between the tranny and t-case. If you don't have the bleed hole then you don't need sealer.

Here is a pic of a V8 tranny WITHOUT the bleed hole. Sorry I forgot to get a pick of one that does have it.

 
#9 ·
BTW both Jeeps were 1993 V8 models. I was swapping t-cases as one one going to be my daily driver and it had a bad NP249. The other was my offroad rig and had a good NP249. I wanted the good NP249 in the daily driver but when I put it back together it leaked. Took it back apart and found the bleed hole. Sealed up the mating surface with RTV and all was good.

Later I took the t-case out of the offroad rig again to replace it with a NP249 and noticed that it didn't have a bleed hole like the other one. Go figure.... Both '93 V8 limited models, one had 3.55 gears(bleed hole) the other had 3.73s with the upcountry package(no bleed hole).


If you do pull the t-case again and find a bleed hole please snap a pic of it for me so I can add it to my collection.
 
#10 ·
FWIW I had the exact same problem when putting an ax-5 in a wrangler. I ended up having to change the rear section of housing on the trans because it was recessed differently. I know this was an ax-5 and np-231 but could be something similar going on with yours. The np-231 used something like 41 different input shaft combinations. So this could very well be a possiblity with your 242.
 
#12 ·
Sorry, for the confusion. Every time the t-case seal was replaced, the transmission seal was also replaced.

I have no idea about the bleed hole, I thought that maybe it needed to be sealed, but I didn't see and factory sealant on there at all. Even if I did seal it, wouldn't fluid just build up in that area until something gave out?
 
#14 ·
That pic is from the ZJ that didn't need to have the t-case/tranny RTV'd. The one that did had a hole drilled DIRECTLY below the output shaft in the small rectangular cavity, in line with the tranny output shaft. It also didn't have the drain hole in the bottom of the case which is what you are reffering to. That missing drain hole was what first alerted me to the fact that something was different from the other Jeep I worked on.

Just because you havn't seen it doesn't mean it doesn't exist. Also remember when working on a V8 Grand Cherokee you are actually working on a DODGE.

I pulled over a dozen XJ and ZJ t-cases. That was the only one I've encountered like that. I just figured it was a weird Dodge thing. I drove that ZJ for two years after that before selling it. Never leaked there or gave any problems.
 
#15 ·
I'm not really understanding what your saying. I would think that the transmission shop it's at would have caught that if it was needed, but who knows.

Still open to ideas, t-case comes out again today to see if I can find anything.
 
#18 ·
Yes. Here's what happened: When I started the swap I had planned on doing the whole thing, including both input shaft removals/installs. After I got the 249 out of the jeep I pulled the input shaft out and decided that I wanted to have a professional install it into the 242.

So, I took it down to an offroad shop that would swap it for me for $125. So, I took it down there, and when I got it back I did not measure the input shaft at all (stupid, I know), I just put the case in my Jeep, and thats when the leaking started.

Turns out, the shop that I had it at made mixed up the two input shafts somehow, and he ended up just putting in the original 242 input shaft into 242(instead of the 249 shaft into the 242). So, the .84" input shaft could not reach the seal, and was leaking.

Anyway, I took the case back up to the shop that messed it up, and he fixed it for me.

So, $600+ later, my Jeep is back in service. Err, well I should be getting it back from the transmission shop (who is installing the case now) tomorrow, and I don't see why it wouldn't work. It has taken incredibly long for the shops that have been working on it to do the work, but oh well. Live and learn I guess.
 
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