NP-242 Transfer case binding harshly, need it fixed before snow!

'89 Jeep Cherokee with a 1990 AX15 transmission and a 1991 NP-242 transfer case.

When I put the 4wd selector in full-time mode, and I make a sharp turn in neutral, it turns just fine, no binding or anything. However, if I take a sharp turn in gear and give it a little gas, the whole Jeep starts to hop and bounce around the turn. This doesn't happen in 2wd. If I try the same thing in part-time mode, the Jeep binds completely and stops turning altogether, even in neutral, which it should.

Another symptom is when I'm driving down the road, even going perfectly straight, about every 20 seconds I'll get a bad shudder from underneath the vehicle. This happens both in full-time and in part-time, but not in 2wd. I have it set up so the front driveshaft spins all the time, so it's only happening when the front axle is actually getting power.

When any of these happens, I don't hear any grinding noise or bad noises, just really harsh shudders. The full-time or part-time lights stay on and don't flicker, and the transfer case lever stays in place and has no abnormal vibration or shock.

What could it be? Transfer case shift forks? That would be rare. Front axle innards screwed up maybe? U-Joints? I'm going to take it to a driveline shop and get them to check it out, but in the meantime, does anyone have any ideas?

Anybody?

I think that you are in 4X4PT mode. The 242 can be in PT mode even though the light says otherwise.
The way I do it, I go from stopped FWD or reverse slowly with pressure on the handle. If I don't hear the characteristic "tick" from the TC that means the shift has happened, I'll reverse. To make sure that I am indeed in 2X4 or 4X4FT, while moving slowly, I turn sharply and put the tranny in N. Any binding or slowing down, means I am still stuck in 4X4PT.

I don't think so, because if I jack up the front end, only the front tires will spin. And it won't stop completley in a tight turn, itll jop and jerk around if I give it gas. Front axle U joints maybe?

mattbred said:

I don't think so, because if I jack up the front end, only the front tires will spin. And it won't stop completley in a tight turn, itll jop and jerk around if I give it gas. Front axle U joints maybe?

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Possibly, the early U joints wear out a lot faster than the later models. I used to have an early XJ that ate them up fast.

Actually you know what, when I still had my NP231 I had an audible vibration whenever I put it in 4x4. After switching out the NP231 for the NP242, I replaced the front driveshaft as well, and the exact same vibration is still there. Only when in 4x4. It's either a Jeep thing, or the U joints are only acting up under load.

Surely someone would know why I'm only getting a vibration when in 4x4?

The front driveshaft spins all the time, so it's only when the front end is under load.

when under load i would suspect axle ujoints or side/spider gears when turning.

You have a front locker in it?

I'm thinking axle u-joints. Mine would whistle in 2WD but squeal like a stuck pig in 4WD.

No locker, no loud noises just a vibration only present in 4x4 that you can feel and hear. Kinda like when you're in too high of a gear at really low RPM's.

This brings up a quick question, how do you know if your u-joints are bad?

~Scott

look for corrosion, spin the wheel, etc

Okay update!

I jacked up the front end so that both wheels were off the ground, and spinning the wheels normally at full lock the U Joints seemed fine. However I started the jeep and put it in full time 4x4, and at full lock when I release the clutch out all the way I get this horrible HORRIBLE knocking, clanging and banging sound from underneath the jeep. I don't have anyone to help me diagnose it yet, but there's definitely a lot of banging of some sorts from under there. Going straight there's no noise but it gets progressively worse the more you turn it, and at full lock the entire jeep is shaking with every bang.

mattbred said:

Okay update!

I jacked up the front end so that both wheels were off the ground, and spinning the wheels normally at full lock the U Joints seemed fine. However I started the jeep and put it in full time 4x4, and at full lock when I release the clutch out all the way I get this horrible HORRIBLE knocking, clanging and banging sound from underneath the jeep. I don't have anyone to help me diagnose it yet, but there's definitely a lot of banging of some sorts from under there. Going straight there's no noise but it gets progressively worse the more you turn it, and at full lock the entire jeep is shaking with every bang.

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To me it sounds like a TC problem.
Pull the TC service plugs and look at the gear teeth and the chain for too much slack. Refill with new ATF.

xjman96 said:

To me it sounds like a TC problem.
Pull the TC service plugs and look at the gear teeth and the chain for too much slack. Refill with new ATF.

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I had the t-case apart when I did the swap and it didn't look like it had much slack in the chain. I don't hear the chain rubbing at all, either.

I just don't see why it would be a t-case chain problem when the only thing I'm doing is turning the wheel. It almost sounds like a front differential problem.

Okay it turns out the bucking I had when I jacked up the front end was the rear driveshaft turning back and forth trying to move. It only really tries to turn when I turn at full lock however. Should that be happening? Do I possibley have a screwed up transfer case?

Edit: I might have figured it out. At full lock, perhaps the U-Joints are binding, causing the front end to resist more which makes the transfercase want to push the read end?

Seeing as how it is a differential, it wants to put power to the weakest spot. Maybe at a certain speed, at a certain tightness of turning, the U Joint is binding causing it to want to send power to the rear driveshaft. The wheel turns fine by hand at full lock, but that isn't going very fast. That's the only thing I can think of that would make it want to turn the rear driveshaft when I turn the wheels - what else would make it do that?

so you have it in 4wd with only the front wheels off the ground? dosent sound like a good thing to do even with the 242

kennzz05 said:

so you have it in 4wd with only the front wheels off the ground? dosent sound like a good thing to do even with the 242

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Yes, I know I know, I jsut didn't have enough equipment at the time to jack up all four wheels. Plus the ebrake was on nice and tight so the engine would stall or I would push the clutch in before anything happend.