Zenroth

Hey all, hoping for insight here. Full time 4x4 mode went out while driving the other day, just continually whirls loudly, no power seems to get delivered to either axle. Part time and low seem to continue to work fine.
Anyways after looking into this a bit, it sounded like the shift fork pads were likely worn/destroyed/etc. So I decided to do a rebuild on the np242, put in all new bearings, new needles, new seals, new chain, new fork pads (1-2 fork pads were indeed shot inside), new oil pump, etc.
I also went ahead and replaced all the u-joints on both front and rear drive shafts, and the centering yoke as well, as all of them were seemingly pretty shot.

Anyways Full time 4x4 is doing the exact same thing as before rebuilding the t-case. During the process I did indeed find some metal bits/etc, but nothing that seemed like it should have needed replacing beyond what was already done.
I haven't tried adjusting the shift linkage yet, but just shifting through the t-case gears everything seems to be pretty spot on from 2wd the whole way down to part time low. Indicator lights come on at the right positions and stay on solid, etc.

I'll certainly try adjusting the shift linkage here at some point, but after digging more it sounds like it might just be the differential inside the np242 itself with some sort of internal wear/damage?

Any ideas?

Cheers

downs

What did the differential mechanism look like when you removed it? I wouldn't get too worried about it until you do a linkage adjustment and verify. Doesn't take long to do.

derf

Did you test everything as you were putting it back together? Did you try manually shifting the case through all 5 positions and check to see that everything did what it was supposed to?

Zenroth

Alright went and adjusted the linkage. Shifting down fully into 4 low is easier. Played around a bit with trying to get 4 wheel full to engage, but no go. In drive and reverse we just have whirling humming and no power. Switching to park makes an odd grindy type sound that is hard to describe and the whirling/humming stops.

Part time high, and low continue to work absolutely fine after the adjustment as well.

Differential mechanism looked okay from what I recall, but I only had it separated from the main shaft for a tiny bit of time to replace the needle bearings on the shaft.

I did run through the gear selections on the bench, and it seemed to shift into each okay and depending on the gear selection spinning things by hand would engage the front output shaft as well/etc.

derf

The grinding sound is the parking prawl in the transmission. The output shaft in the transmission is free spinning into the transfer case in full time. So when you drop the transmission into park it will grind just a little until the tail shaft stops spinning.

Is 2WD really acting like 2WD? Can you jack up one front tire and free spin it when in park in 2WD? If not, you may not have gotten the whole assembly back together right and it's staying in locked 4WD. There are several things that could have gone wrong with the reassembly. Did you get the roll pin back in the shift rail? Did you end up putting the shift collar on upside down? What condition were the teeth on that collar in?

Zenroth

2WD seems fine, and just tested now, and indeed i'm able to jack up a single front tire and freely spin it, with the transfer case in 2wd and the jeep in park.
I was able to pry and pop the forks/shaft out without extracting the pin. I do remember spending a fair bit of time reassembly that part along with the shift collars and pads. Pretty sure all of that went back together correctly. Kinda wishing I had taken pictures during reassembly now..

The shift collar teeth are one of the pieces I do believe had a nick or two out of some of the outer teeth. Nothing really sever though that I recall.

lawsoncl

You also verified that the tire doesn't spin with the xfer case in parttime 4wd? Just wondering if your problem isn't the xfer case but rather a blown front diff.

Zenroth

I didn't.. I'll check that today. Might make a lot of sense actually, i'll be kicking myself if i rebuilt the t-case and its actually the front axle that is out. Though the t-case obviously needed some love too, with 2-3 shift pads broken/apart, some metal bits in there, and what not, though most of the bearings seemed just fine.

Zenroth

Okay so.. got back under and looked at the axle a bunch. Found which I never knew that there is a disconnected CAD on the axle, and sure enough there is no vacuum line. I dropped the CAD cover and slide over the damn axle shaft combiner ring, and with the jeep on 4 jack stands, I have 4 wheel drive in all positions. Though shifting between them is clunking hard, hopefully thats just from being up on jack stands. Have no idea how 4 wheel drive was working previously, mysteries of an undocumented and not greatly maintained xj only picked up a few months ago.

derf

That sucks. It sounds like there's still something up with the case. It may have to come back out unfortunately.

Zenroth

Well locked the CAD system in place and bolted it back up. Still had some clunking with the transfer case gear shifts. Pulled it back in, did another linkage adjustment, and realized earlier I had loosened up the shift detent spring/bolt when trying to shift the transfer case manually from underneath with the linkage disconnected. Tightened back up the shift detent and everything is working, no more clunking when shifting the t-case.

Makes me wonder if I ever needed to rebuild the t-case at all, though some of the fork pads were indeed shot, so I guess there is that, and a rebuild at 130k miles on it, with obviously poor maintenance probably isn't a bad thing.

Thanks everyone.

lawsoncl

I didn't think any of the 242 setups came with an axle disconnect because the 242 doesn't have a provision for switching vacuum? I have a 242 to swap into my heap, and I planned to just lock the CAD over. To test having the CAD engaged full time in 2wd, I temporarily rearranged the vac lines to keep it engaged. Maybe the PO just monkeyed with the vac lines instead of mechanically locking it in place? I wouldn't worry about clunking in/out of 4-full on jackstands, since the wheels are all spinning at the same speed. I bet it's fine on the ground

Zenroth

I'm not sure on the CAD and 242 mix, I am pretty sure of one of the POs seemingly swapped front and rear axles though. Learned that after ordering 500$ worth of front and rear brake parts from rock auto, and pretty much none of it fitting. Ended up needing to match up parts from 90+ years, vs 88.

This thing has been a journey of discovery really. Body and interior was clean, it ran alright, but had a host of seemingly minor issues like no oil gauge, speedo bouncing, heat not blowing, brakes feeling soft, radio stolen and wires cut, etc.
After digging into it for various repairs, i've found the swapped axles, charcoal canister/egr/etc all butchered, no vacuum ball, transmission mount threads need re-tapped badly, major fuel economy issues, now the t-case issues, etc. The previous PO seemed to mostly just use it as a winter only rig for their kid, and went on a lot about it being a weird jeep due to being an 88 and renix heh.