WTF did I do wrong?

91 xj 4.0 aw4 np231

I installed my PORC SYE after I lifted her back in December. Upon installation, I did not have a rear driveshaft and eagerly wanted to drive it because I had the tcase out for a couple days. I drove out of my drive way with it in four wheel (only front driveshaft) and when I hit about 30mph, i heard the tcase slip and just grind with no furthr movement. I put it in two wheel then back to 4hi, engaged, drove a little, 3 seconds later slipped and grinded again. ignored it and did not drive it again until i got a front DS out of a ZJ and usd it for the rear.

I have a disco 30 with the vacuum switch on the tcase, therefore I had to grind the shaft in the case. I grinded it down to an inch per instruction, but the speedo housing did not seem flush enough with it fully engaged, so i took a little more off until it was rather flush (although still not completely).

I wheeled a little the past six months and it has been working fine, just a little slip and grind here and there. Yesterday, I went for a hill climb and did not have 4wd, axle was engaged (PART TIME light), but no front tire movement, which led me to believe the vacuum was working corectly, but the case wasn't engaging. I usually could crawl up the hill from past experience, but yesterday my rear tires were just spinning; couldn't even get half way up.

I am 95% sure i installed teh SYE correctly as i made sure to take my time on it. Ever since i did, i have had 4wd act really screwy. I readjusted the handle after I reinstalled the case becase it just did not feel like it was engaging correctly.

My thought is that the shifting shaft? inside the case is not grinded down enough so the shaft is just pushing against the speedo housing when engagd, not allowing the gears to mesh up correctly. I have seen absolutely no problems in 2hi since the install.
PLEASE HELP!!! I am goin wheel in july and obviously need to splash some mud around and would rather not go through the hassle of removing the case again. Thanks in advance.

I would double check you haven't broken the aluminum shift fork in the CAD.

I went through like 3-4 of those things.

Take it all the way...the hairline fractures are hard to see if you don't. A little bit of flexing can keep the axle from engaging.

Never thought of that. The part time light lights up like it should though. Would it still slide over and activate the switch in the axle if it was broken? I still would tnd to think that it points more at the case though. I will tak a look at the shift fork when I get home. (MID POST THOUGHT) Are you talking about the one in the case or the one in the axle?

he is talking about your fork in the front axle, i just broke mine and it will not shift into 4 hi, i can shift to 4lo and back to 4hi and it stays ingaged. also my buddy's was acting up on sunday, kept popping out of 4wd, just hes rear wheels were spinning and come to find out afer getting home his vaccume lines had melted on something causing the vaccume motor to just kind of do what it wanted to do.

My problem definitely has nothing to do wih vacuum, as the PART TIME light comes on and goes off like it should. I REALLY hope it is just the shift fork, that would make me feel alot better. Come to think of it, it was awfully quiet when i shifted into 4wd. I can usually hear it shift into place in the axle... I really hope it is that. Will repost when I get off of work.

Did you cut the mode fork shaft 1" shorter or until 1" extends beyond the rear case half? The rod should extend about 1" out of the rear half of the transfer case when farthest out.

Check your linkage. If I just go from 2hi to 4hi, sometimes things act like you're describing. If I go to 4lo (while stopped), and then back to 4hi, all is well. I know I "stretched" my linkage when I lowered the drivetrain before I disco'd the t-case linkage.

Now that I know what's going on, I can usually fully engage 4hi without having to go low first. Someday, I'll get the Novak linkage, but right now, not a necessity.

Steve

I cut the shaft more than 1" from the case (didn't measure the final length, only until it was enough to sit flush.) 1" was too long, not allowing the speedo housing to sit flush when engaged into 4wheel. It still didnt fit perfectly flush (I am anal), but it was damn close.

Adjusting the linkage was the first thing I did after the test run in 4hi with just the front driveshaft, as a response to the grinding (1/8" of an inch shim in between the shift lever, then tightened.)
Did not get a chance to check out the CAD fork as I am very busy, but should have time tomorrow. Hopefully, this suggestion is the correct one. but since the tcase has been grinding at some points, I still feel this is the root of my problems. However, I tend to think of the worst possible scenario.

No leaks from the yoke seal or anywhere else on the case, will also check fluid level/appearance tomorrow.

Thanks for all of your inputs! Keep 'em comin!

if you hear the grinding from the t-case like you for sure know its coming from it i wouldnt bother with the CAD fork its gonna be the t-case. the CAD fork wont cause grinding noise from the t-case

Drain the ATF from the TC and look for flakes of metal. If you are grinding you might have a big problem.

I haven't heard it grind in a couple months; I thought the previous grinding was what had caused this sudden non-engaging moment. I thought this because the PART TIME light lit up (CAD sliding over) which led me to think that the gears might have worn down in the case or something. DEFINITELY thinking that the CAD fork has something to do with it.

I am also thinking that the passenger side axle shaft did not slide in right when I changed the u-joint a week ago.

I just don't know what to think right now. Is it possible that once I reinstalled the case the gears just had to get used to the newer, bigger HD SYE shaft? Or did drivning it with only the front shaft have something to do with it? Really helpful; always is. This is why I love

Sooooo just got finished taking apart the CAD. Everything looks normal. With the CAD assembly off, I rotated the driveshaft; the axle shaft coming from the pumpkin was spinning with the rotation...normal...slid the collar over and driveshaft rotation stopped...normal...put it in 4hi with the collar off, driveshaft caught and saw movement in the rear DS with the movement of the front one...normal...Vacuum actuator slid back and forth with vacuum pressure once off the vehicle...normal...Fork was clean, no cracks or anything. It was, however, loose (moved a little from side to side)

Took her for a spin. rear wheels just spinning. Mud in the rear treads and mudflaps, but not a trace in the front. I'm at a loss. pleaseee helpp meee

bdahlg said:

(moved a little from side to side)

Click to expand...

It shouldn't.

Double check that fork. Seriously. Take the thing off of the shaft. I couldn't even tell mine was broken until I took it off. The crack usually begins around the part that slides over the shaft.

MoparManiac said:

It shouldn't.

Double check that fork. Seriously. Take the thing off of the shaft. I couldn't even tell mine was broken until I took it off. The crack usually begins around the part that slides over the shaft.

Click to expand...

Jeep had an updated, stronger fork available because the originals could crack and/or bend and it was not easily detected except by close examination.

Or you can get a cast iron one out of the CAD of an 85-93 Dodge D44.

Bolts right in.

Will definitely double check the fork; I thought it was a little wierd that it was moving since the last time I had the assembly off it was solid.

On another note, looked underneath the jeep when it was stuck (lifted 4.5" easy to do), revved a little in gear with my hand, front driveshaft was spinning while the front tires did nothing. At least I know the transfer case is not my problem. Would the fork not shifting all the way cause this? I guess I could see it in theory, but since it does not sound like its struggling to engage (if it was bending there would be some force against the collar) and I know the actuator is doing its job because the light illuminates.

Broken spider gear or something in the differential? Narrow down the possibilities for me. I know little about gears, but I know a lot of you know a ton about them.

Pop the cover on the front diff and see what kind of shape your gears are in. You should have the pinion gear in the back of the housing driving the ring gear mounted to the carrier, the carrier should have two side gears and two spider gears inside it. None should be missing teeth, etc.

Sounds like the fork is broken.

Stop wasting time and pull it off the shaft.

You're just spinning the intermediate shaft (no resistance so all the power goes here) and it's not connected to the "outer" inner passenger side shaft.

A broken shift fork won't work at all.

I understand how differentials work and understand that the intermediate shaft spinning would definitely cause these symptoms. Most likely the problem. I will pull it off when I get back from work. The stealership wants $60 for a new one. I can source a cheaper one online for sure. Anyone know where to acquire a new one? I would definitely want a stronger one that was stated a couple posts ago.

Can someone (MoparManiac if you could chime in, since you seem to have a lot of knowledge/experience with this problem) just clarify how a broken fork could not shift at all? I'm just wondering this because the shaft has to slide all the way over to hit the FULL TIME switch (which is working like its suppsed to.) The fork did slid back and forth when vacuum was applied, it was just a little loose. Even with a broken fork, why wouldn't I hear SOME noise from the collar trying to slide over the intermediate? Surely there would be some force applied from the fork to the collar if the shaft is sliding all the way over to hit the switch. Or am I just on the wrong thought process? Again, thanks for all your help.

Get a cast iron one from an 85-93 Dodge D44. I went through 3 aluminum forks before switching to the dodge cast iron fork.

The fork is flexing. You can't put the same kind of pressure on the fork with your hand that the vacuum diaphragm/shaft setup is applying to it. IF there is even a hairline crack around the part that connects to the shaft, then it WILL flex under load and not move the collar. You may not hear a grinding sound or anything, who knows. I'm not 100% on the specifics.