231 has me stumped, won't go into 4wd

Ok so after taking my case apart and replacing the oil slinger and pickup I have put everything back together and it shifts perfectly, except for the shifter being in 2wd and the drivetrain in 4wd. The shifter works great and the linkage is fine but when the shifter is in 2wd I am in 4wd. I can shift to any other location and it works fine, neutral, and low range work where they are supposed to it just stays in 4hi when in 2wd selection.
I have taken this case apart over two dozen times comparing to two other 231 transfer cases I have here and everything is identical and where it is supposed to be. I am totally stumped here and would sure like to drive it to work tomorrow.

I am working on a 1998 xj 4.0,AW4, 231 with Advance Adapters SYE, hope someone can shed some light on this.

Don't take offense but, did you adjust the shift linkage to make the lever match the right gears?

What condition were the nylon pads on the shift forks?

old_man said:

What condition were the nylon pads on the shift forks?

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this.

i tore down a case 4 times for travisk on here for the same reason before we noticed the shift fork pads were hosed and it had allowed the shift shaft to wallow out the hole it rides in on the front half of the case, a new case half fixed the problem. the pads are only a few bucks at the dealer it's worth replacing them no matter what they look like just because you have the case open.

I never had to touch the linkage as I only removed the rear half of the case so I don't think that is the problem. No offense taken. The tabs were worn so I replaced with new ones on both forks. What I don't understand is when I drove the jeep into the garage it shifted and did its thing normally, going into 2wd that is.
I took the back half off, replaced the oil slinger and pickup, replaced the tabs, and slapped her back together. That was last Thursday and every night since then I have been messing with this thing and getting nowhere.

I guess a little background on as to "why" I took the case apart. Last week Wednesday I was on my way home from work which is about 17 miles away and had it in 4wd the entire time going around 55-60 which I have done many many times before and no problems. While taking my off ramp I let off the gas and that is when the nasty grinding noise came up, I shifted into 2wd and it went away. As I gained speed in 2wd I could hear a faint noise barely noticeable, I shifted into 4wd and about two miles down the road it started to grind again so back to 2wd home.
I took off the front driveshaft the next morning and could not get the noise to replicate so I replaced the front shaft and left for work. A few miles into my ride I had to use 4wd and about five or six miles I get the grinding noise again so I turn around and go home. Now I dig into the case and find the sprocket on the main shaft for the 4wd is chewed up a little along with the syncro ring that slides over to it and locks it in 4wd. I noticed a clogged screen so I replaced the screen, tube, and oil slinger thinking that it might have been plugged and not oiling properly.

Now ever since then I have been fighting with trying to get 2wd in the t/c when my shifter is in 2wd. It drives around fine, shifts fine into the other options but just won't go into 2wd.

Have you tried getting underneath and physically putting it into 2WD?

Yes I have and it is where it is supposed to be, it cannot go any further on the t/c.

Flip the synchro/shift ring around. I fought one forever until I realized I had installed it backwards. It is just different enough that if backwards it will not disengage 4x4 even if in 2wd position.

It is installed the proper way, i cracked apart two other 231 cases to verify.

Worked before + does not work now = you did something to make it not work! You may have to pull the entire case off, pull it apart looking for your mistake. I would buy a rebuild kit and have at it. :spin1:

Shift collar/hub installed backwards or linkage problem.

Pulled the case out and cracked it apart. Again everything is where it is supposed to be, nothing is backwards and the linkage is correct. So I am swapping out cases this morning we will see what happens.

Well still stumped. I went and picked up another known good 231 and made sure it shifted and worked properly before I left. I get home and check it out again on the bench and it works and shifts properly. So I crack it apart and leave the shift forks and everything in there except the chain, main shaft and front wheel drive sprocket.

I proceed to put the back half on that has my SYE installed on and put it together. I put it together with it in 4lo and shifted it to the 2wd position now that it is bolted together and it still will not engage 2wd! Only way it will is if the case is 1/8 an inch separated. So I separated it again and put the linkage in 2wd and bolted it back together. I can shift it to all ranges but still in the 2wd selection it is locked in 4wd. I have been comparing everything to another case here and everything looks the same, measures the same, and all goes together the same but yet no 2wd.

I have been in 231 cases many times in the past eight years so these are not new to me, which baffles me why I am having so many problems.

you're not forgetting the return spring, are you? The spring is how the mode fork is returned to the 2wd position.

Also i have seen many times where the range fork is not engaged correctly into the range gear slot when the case is reassembled.

Also, the rearmost mainshaft snap ring has to be in place for the case to shift correctly. if left out it will shift oddly, or very difficult.

Digger87xj said:

you're not forgetting the return spring, are you? The spring is how the mode fork is returned to the 2wd position.

Also i have seen many times where the range fork is not engaged correctly into the range gear slot when the case is reassembled.

Also, the rearmost mainshaft snap ring has to be in place for the case to shift correctly. if left out it will shift oddly, or very difficult.

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The spring is there and the mode and range fork are in there spots when assembled. The snap ring on the main shaft you are referring to is that inside the speedo housing behind the yoke going to the rear driveshaft?

snap ring goes rearward of the mainshaft support bearing. When left out, or misplaced the mainshaft can move forward and aft about 1/2 inch.

But now thinking, with an SYE, the bolt-on yoke takes the place (does the job of) of the snap ring