Grinding sound in 4wd

Winter is in full swing here, and the other day I had to engage my 4Hi to get out of a nasty patch of ice. When engaging and at sporadic intervals afterwards, my Jeep let off a loud grinding sound, esp. when making any sort of turn.

it's a '95 XJ - Automatic, with a 4.0L HO Engine, NP231 TC, not sure about much else. This Jeep had an issue with a particularly stubborn broken motor mount bolt, and sat on the side of a family member's house for a few years before I had it towed to the shop to get it fixed. I'm just now getting around to inspecting the engine, etc. - so far it runs great, even with 166k miles on it.

Now, being the idiot that I can sometimes be, I remembered after this happened a leak I'd spotted from the TC a few weeks earlier. I knew there was an issue there before, and I'm fairly sure it's a bad seal, and I wrongly assumed that my mechanic had paid attention to what I told him and had fixed the problem - especially since he'd replaced a seal on the transmission at the same time.

So, could this be caused by a lack of fluid in the TC? If the gears aren't being lubricated, it seems the most logical culprit.

Anyone else have any ideas?

E

Is it slipping out of gear when it's making this noise?

Sounds like 4WD wasn't engaged completely. I had a 98' that would do that occasionally only in 4H.

Get underneath and lube the shift linkages. Get inside and work them, then back underneath and lube them some more.

They may able be slightly out of adjustment.

Lastly, and I would look into this after making sure the linkages and adjustment have been checked/done.

The 231 uses nylon bushings on the shift forks (internal). They wear out and make positive shifting an iffy affair.

Lastly, I have heard of drive chains (internal) being so loose that they slip, making a grinding sound.

Lowrange2 said:

Is it slipping out of gear when it's making this noise?

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When I first engaged, it felt like it might be slipping. I had to drive a short distance out of necessity, and it wouldn't do it when I was driving straight, but seemed to start up again when I went to make a turn. Not every time, but consistently enough. Not sure what sort of difference that makes.

WB9YZU said:

Sounds like 4WD wasn't engaged completely. I had a 98' that would do that occasionally only in 4H.

Get underneath and lube the shift linkages. Get inside and work them, then back underneath and lube them some more.

They may able be slightly out of adjustment.

Lastly, and I would look into this after making sure the linkages and adjustment have been checked/done.

The 231 uses nylon bushings on the shift forks (internal). They wear out and make positive shifting an iffy affair.

Lastly, I have heard of drive chains (internal) being so loose that they slip, making a grinding sound.

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That was one of my first thoughts, that it may not be engaging fully. Thanks, I'll try that first and see what difference it makes.

Just to clarify, to lube the shifter linkages - you mean to engage the 4wd, correct? Or am I misinterpreting you?

If you're not using 4WD often, the linkages can bind up, and one way to keep things limber is simply to sit there (engine off) and run the shifter through its cycle many times. In my experience 40 seems like the magic number. If you run from 2 hi to 4 low 40 times in a row, I bet your linkage will be nice and limber.

If the linkage is adjusted wrong in one direction it will not shift far enough to engage 4 high, but it has to be pretty bad for this to happen. It's more likely to show up as missing 4 low at the far end. If it's adjusted wrong in the other direction, you can shift past the 4 high spot, and it will grind. So one thing to try is to wiggle the shifter a bit (after it's nicely loosened up), and see if you can feel the 4 high detent.

You should also check your front axle universal joints. If they're worn out you'll get all sorts of noises when you turn, and if one is really bad it will tend to hop and skip as it binds and lets go, which can feel almost like popping out of gear. When they get that bad, there's a risk that one will break and trash the shaft yoke when it jams.

Matthew Currie said:

If you're not using 4WD often, the linkages can bind up, and one way to keep things limber is simply to sit there (engine off) and run the shifter through its cycle many times. In my experience 40 seems like the magic number. If you run from 2 hi to 4 low 40 times in a row, I bet your linkage will be nice and limber.

If the linkage is adjusted wrong in one direction it will not shift far enough to engage 4 high, but it has to be pretty bad for this to happen. It's more likely to show up as missing 4 low at the far end. If it's adjusted wrong in the other direction, you can shift past the 4 high spot, and it will grind. So one thing to try is to wiggle the shifter a bit (after it's nicely loosened up), and see if you can feel the 4 high detent.

You should also check your front axle universal joints. If they're worn out you'll get all sorts of noises when you turn, and if one is really bad it will tend to hop and skip as it binds and lets go, which can feel almost like popping out of gear. When they get that bad, there's a risk that one will break and trash the shaft yoke when it jams.

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First time I've had to use the 4WD since I took it in to fix the motor mount bolt, so it hasn't been used in quite a long time indeed. I'm still worried about the possibility of there not being fluid in the T-Case, since it sat for so long and had to be filled up rather often before.

I really couldn't hope for it to be much simpler than what you're saying though, so I'll definitely give it a try and see if I note an improvement.

I have a basic idea of how to check the U-Joints, but anything specific I should be looking for? They're a bit worn and seem to have some surface rust last time I looked, but anything more specific I should be looking for would be helpful. My experience with Jeeps is unfortunately limited, (unless you count the complete rebuild on an old Willy CJ-5 I did with my dad as a kid). I'm mechanically inclined, but I don't remember much as I should.

So I have to ask - is it safe to run the shifter through it's cycle if there's a lack of fluid in the TC, or should I wait until that's been taken care of before I give it a try? Not sure if that's the case or not, but I'd rather not find out the hard way.

Also, @WB9YZU, If I'm to go and lube the shifter linkages, what should I be using for lubricant, and precisely what should I be applying the lube to? I'm sure I can figure it out, but I'd rather know a bit more before I get down there and find out I can't.

Alright, well - I'm really leaning toward there being insufficient or bad fluid in the TC based on what I know. Going to check that first before I do anything else, if that doesn't fix it, I'll move on down the line and try the rest of the suggestions. I'll probably just go ahead and lube the shifter linkages for the heck of it, since they probably need it anyway, but I know she probably needs fluid and a new seal.

Might have the internals checked out by someone more knowledgeable while I'm at it. If anyone else has any ideas, I'd be happy to hear 'em.

I'll let you guys know what the verdict is.

If it's worse on turns I would look at the u-joints. They are loaded differently in 2WD (coast) and 4WD (drive)

ehall said:

If it's worse on turns I would look at the u-joints. They are loaded differently in 2WD (coast) and 4WD (drive)

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After a bit of research, I'm kind of wondering if that might be exactly what's going on.

Could the front u-joints going bad cause sporadic Death Wobble? Been dealing with that the last few months periodically, wrote it off as an alignment issue and my balding tires (in the process of getting replaced).

I'm going to take a look and see what I can tell. Doubt I'll be able to check for play since I don't have easy access to a jack atm (only real thing not in storage is my engine lift, sadly).

Well, I think I'm on to something. A troublesome U-Joint makes perfect sense with the other problems I've been having so it's a very likely culprit. And it does seem like they could make the sound I've been hearing, which'd only occur when the front axle was engaged.

Now, if it is a U-Joint, I'm going to be one very pissed off customer next time I see my mechanic. If he didn't check the U-Joints for play when I had the previous $1600 in repairs done, well, he's either incredibly stupid or trying to pull one over on me by doing the bare minimum. Serves me right though, should've done it myself. Bad enough he let me drive it from the shop with almost no oil in it, and day before yesterday I notice he didn't change the oil filter and it's leaking from the O-ring - should've been a warning sign right there. :banghead:

We're going to have a fun discussion next time I get down to the shop, that's for sure.

If I get the U-Joints checked and (presumably) replaced and that fixes it, at least I'll have learned my lesson, I suppose.

Sorry for the multiple posts, been wracking my brain over this for a while now and I'm frustrated beyond belief at this point.

XJLogic said:

After a bit of research, I'm kind of wondering if that might be exactly what's going on.

Could the front u-joints going bad cause sporadic Death Wobble? Been dealing with that the last few months periodically, wrote it off as an alignment issue and my balding tires (in the process of getting replaced).

I'm going to take a look and see what I can tell. Doubt I'll be able to check for play since I don't have easy access to a jack atm (only real thing not in storage is my engine lift, sadly).

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Yes, you can get some sporadic death wobble with bad u-joints, as well as other bad behavior. Of course if you have balding tires and other problems they'll all conspire together, so it can be hard to figure out what's causing what.

Most of what you need to do to check the u-joints is just to reach in and see if there's any play or looseness. There shouldn't be. A little bit can be tolerated for a while, but a lot can get critical as the two halves of the joint will tend to jam and unjam and eventually can cause real damage. Before they get loose, they can also get stiff. To test for that, you just jack up one wheel at a time by the axle, turn the steering to full lock, and rotate the wheel. If it binds and is hard to turn, you have a bad joint. You will also probably hear a loose joint clacking when you do this, so if you're not in the mood to get right down on the ground and stick your fingers into the knuckles, you could start with the jack test.

Thanks matt,

Going to take some time this weekend to see if I can track down my floor jack, if not I'll have to commandeer one so I can get down there and take a look. Seems like the U-Joints are a good place to start, and I'll check what I can of the overall drivetrain while I'm down there, and pick up some ATF and so on.

For a while I thought the tires and alignment alone might be conspiring together to cause the DW, especially since it was worst when my mechanic sent the Jeep back with the air pressure far too low. It stopped for a while after I put some air in them, but then started back up again on the highway - happened on a turn, no less. Same place the 4WD acts up.

I'm waiting on reg. anyway, and have the luxury of not having to commute everyday (I'm an independent contractor), so if all else fails maybe I'll see if I can track down a good Jeep/4WD mechanic to do a more thorough inspection. Hopefully it doesn't come to that, but I probably should find someone who's knowledge fills the gaps in mine anyway.