Thanks all in advance for any in sight you may have to whats going on...

I have been working on the transfer case (NP231) in my 01 XJ now for about a month and a half chasing down a slippage issue and a popping sound. A little back story, I bought this XJ and on my first time out with it I noticed that I struggled to get it into 4lo and it would slip out sometime all the way into neutral. In addition there is a loud popping noise in 4 LO and 4 HI but not in 2WD. In 2WD everything is fine, I can run highway speeds, put it to the floor and create stress on the driveline and still nothing is wrong. However when I would put it in any of the two options for 4X4 I would get a loud popping sound that sounds and feels like it is from the transfer case but me being a vet with 1 ear, I cant locate sounds that well. I pulled the case down and it has a SYE kit on it due to the lift on the jeep so just putting in a stock case was out of the question. I opened it up to find that the bigger of the two shift forks was ground away on one side. I got a new fork and race gear (I think its called) and installed both then put the case back together. I gave it new fluid and went to go test it out in a dirt lot by my house. Same thing was happening. I again had a loud pop sound in 4WD and would slip in and out of 4LO. I am about to take it out again and replace the chain in case that may have stretched and ordered the upgraded shift linkage to replace that and make sure its not that my linkage is off. Other than those two things I can not think of anything that may be causing this and am looking for in sight or help. This level of mechanics is way above what I have done before so any help is appreciated.

 

I think I'd put it back together and find another one. Drive what you have until you can rebuild the "new" one and modify the output shaft.

 

That's essentially what I did, when I replaced the forks with the one I salvaged out of a jeep with about 100k miles on it I tried to replace as much as I could. I never changed the chain over because I figured it would've been fine though. As for all the other parts they were essentially moved into the old broken case to replace its guts. i didn't go as deep as replacing the planetary gear or seals though. Mainly just what you could pull out once opened.

 

I'd go the other way... Put your Output Shaft into a "new" case...

 

Do you see any wear on the inside of the case where the chain rubbed against it? That's the primary way a stretched chain will "show up"...

 

I can try that, I have the other case I sourced the parts from still I would just have to swap everything over.

 

Your popping noises and it slipped out of gear make think that the little teeth end of the "Sliders" that engage the planetary at the front and the 4wd at the rear of the case are worn off, caused by the little plastic pads that go on the shift forks wearing out.

You'll need a pair of Internal Ring Pliers, like these

 

I have a pair of those, are you referring the gear that the two forks wrap around as the "sliders"? I replaced those with the new case's gears during the first attempt at fixing it and none of them had any visible damage or wear.

 

Yeah... I'm used to the 242; it has another piece...

Popping out of 4Lo could be due to the linkage if it's not adjusted properly and you can't move it enough to get it all the way into gear. Other than that, the TCase controls the positions w/ the ball detent on the shift pawl.

 

Gotcha, so you think with replacing the case all the gears i already have replaced and now the chain and upgrading the linkage and ensuring the adjustment is correct that it should be fixed? I mean Im not too sure what after that there would be left to fix lol

 

It's hard to say with the "old" case. Who knows what happened when the SYE was installed. I was going to mention about the possibility of this, or the possibility of that, but it's been a few years now since I've had my 242 apart and well, ignorance is bliss... :-) I think I'd trust a plain jane stock case out of JY more than I would trust the one you're starting with.

Replacing the linkage is never a bad idea; so much better than stock, but I will say that I ended up just removing the shift gate in the cab and shifting by memory, not even worrying about trying to get it synced up with the coverplate. It's possible that the shift get in the cab is your issue, not letting it go all the way into gear... Should be easy enough to find out, IIRC, as once you loosen that bolt and the detent pulls that half the linkage into place, you'll see it move if it was...

 

Ill check this out tonight, I honestly thing that the popping sound may be separate from the slipping issue. When I put it in 4HI the part time light comes on in the gauge cluster but when I shift it to 4LO the full time light does not come on. That makes me think it is the linkage causing the slipping and the the noise is the chain slipping. In theory I should be able to disconnect the linkage, put it in 4LO and it shouldn't slip out but still have the popping sounds.