second opinion

Not sure if this is the right spot for this question or not, but here goes.
First a basic rundown of my Jeep: 88, 4.0, AW4 and 242 t-case, open d30, 8.8 with factory limited slip.
Was out wheeling at Rausch today, and at the end of the day was crawling up a very rocky hill. I made it about 2/3 of the way up and was at a spot where I needed to get on the throttle a little more than I would really like to. The Jeep bounced a little and was followed by a pop, which turned out to be the flange on my 8.8. After being winched the rest of the way up the hill, removing the driveshaft and limping back to the parking lot we got ready to head home. So here's where I'm unsure: I thought that if I put the tcase into fulltime 4wd I would be able to drive home on just the front shaft, but the jeep would not move in any forward gears or reverse. The rear output spins to the point that the speedo will indicate about 25 mph with the engine idling.
We decided to try 4 hi, and the jeep moves forward and reverse. Ok, good to go. On the highway though things were different. I had my foot to the floor and couldn't do more than 50 mph. Two other things were happening on the highway also: the jeep sort of jerks around, and there was a grinding/whining sound coming from under the shifters.
Ended up getting it home on my buddies trailer and got under it tho really take a look at things. I found that the tcase fluid was about 1/4 - 1/2 inch below the fill plug, and it was full when I checked it this week. Also the cross member that the tcase mount is on has been pushed up about 1" in the center.
Now my first thought is the the tcase is shot, either from a shock load when the axle flange was broken, or from being hit/the cross member being bent.
Any thoughts anyone might have on this? Sorry for the long post.

Fulltime 4wd acts like a differential and sends the power to the output with the least resistance - the one without the driveshaft in your case. You would need to use part time 4wd which locks the two outputs together like you found out. That is normal.

The 50mph limit, the grinding, etc is probably a sign that the tcase is about to go. Sounds like a rebuild or replacement is in order.

Get rid of the 242 for a 231. Some people like having the full time 4wd on the street but for jeep your going to wheel the 231 is a much better choice.

As far as the 50 mph limit- Not good.

I've driven front wheel drive in the 4h setting at 65+ with no problem. It's noisy, but fine.

Your case might be on it's way out.

Thanks for the replies.
Limped it to the carwash this morning to get the underside clean, and decided I might as well take it for a test drive and get it up to speed now that my head has cleared a little. There is still a noise that seems to be coming from right under the shifter handles, that sounds like something spinning that is either meshing dry with something else or rubbing up against something. The sound is accompanied by a whine after maybe 30 mph and is a bit louder when on the gas.
Was able to get it up to about 55 mph with about 3/4 throttle and then put it all the way to the floor. The engine instantly went right to 3000 rpms and sat there and the Jeep lost power and started slowing down. That happened for about 5 or so seconds until I lifted and it then seemed to "catch" again.
This has me thinking that maybe it's not the tcase, but the tranny instead. Any thoughts?

that noise in 4 wheel drive sounds reasonable. how often are you in 4 wheel drive at 60 mph? .. i am pretty often, and the t-case is loud.

and yes, it does sound like you may have a transmission problem.

here is a thought that i have. if it was the transmission it wouldnt matter if you were in 2wd 4h full time 4h part time or anything it would act the same but since it works in 4 h part time and not in 2wd that i would have to put money on the tcase not the tranny

there is nothing in the tcase thats going to slip. maybe a streched chain will make the grinding whining noise you are talking about but maybe the tranny finally had it.

So I think my plan of attack for now is going to be to order a new flange for the axle so i can reinstall the rear shaft and be able to drive in 2wd. Then I need to go out this weekend and pull a new crossmember since it needs replaced anyway and see how it drives once everything isn't pushed up an inch. HOPING that maybe some of the linkages are just bound up or that it being pushed up is putting pressure on something somewhere. Seems like a shot in the dark but figure it's the cheapest easiest place to start.

So I have two questions that I'm going to search out the answers for but thought I would post here and maybe someone can help me out.
1. What crossmembers will work with my year, tranny, tcase combo?
2. Will any year AW4 bolt up to my engine and be able to run in my 88? I think the answer to this one is yes, but not 100% sure.
TIA

fasteddieyj said:

So I have two questions that I'm going to search out the answers for but thought I would post here and maybe someone can help me out.
1. What crossmembers will work with my year, tranny, tcase combo?
2. Will any year AW4 bolt up to my engine and be able to run in my 88? I think the answer to this one is yes, but not 100% sure.
TIA

Click to expand...

So I found my answer to the 2nd question. I was basically right. They all bolt up, just some wiring issues.
Still no definitive answer to the first one though. Looks like the biggest difference might be where the crossmember mounts on the frame, not the crossmember itself. Anyone confirm this?

fasteddieyj said:

So I found my answer to the 2nd question. I was basically right. They all bolt up, just some wiring issues.
Still no definitive answer to the first one though. Looks like the biggest difference might be where the crossmember mounts on the frame, not the crossmember itself. Anyone confirm this?

Click to expand...

You can use any AW4 from 87-97, but if you get a 91-97 you will have to get a late model transfer case to go with it. You can NOT use any AW4 98 or newer, as the vehicle speed sensor is not compatible with your electronics.

Your crossmember question is ambiguous. Are you looking for a stock of aftermarket solution? The stock ones are all the same (there is more than one set of holes on the frame, and not all of the transmission mounts are the same). Aftermarket.. look at what the manufacturer says, some are too tight for the NP242 t-case which has a slightly larger housing.

Thanks man. Just looking for a stocker for now so I can get everything back into it's correct location so I can properly evaluate my tranny/tcase issue.

So I might have gotten lucky. Went to the local pull a part today to pull a crossmember, found a 94 with the tranny and tcase removed. Out of the goodness of their heart they left the crossmember sitting right there for me. It was obviously out of a Jeep since it was covered in grease. Got it installed and took her for a test drive. The "grinding" is gone, although it looks like that is normal. Got up to about 70 which is basically all the faster it goes anyway. It still hesitates pretty bad if I floor it at highway speed, or pull out into traffic and really get on it. Thinking thought that this might be an unrelated issue. Gonna check for a possible vacuum leak, pull the cap and rotor, all the tune up items and see if maybe something there isn't the cause.