Derision

I've been trying to track down a noise that I keep hearing coming from the rear passenger side of the Jeep. At least, I presume that's where it is -- being in the driver seat, everything sounds like it's coming from the rear passenger side.

The thing is that every time I think I might've pinned down the noise, what I thought it was, it wasn't.

The noise is a low kind of "whooom" that increases in pitch as the car goes faster. If I didn't know better, I'd think that I had some really awesome, oversized off-road tires that sound all oversized, off-road tire-y whilst on pavement... but I don't. It doesn't make the noise below 25 miles per hour, and is most noticeable between 25-50, with only a little bit of gas being given. If I take my foot off the gas, the sound stops instantly. It does not occur whilst the car is coasting in neutral with the same amount of gas being given. The sound is also independent of engine RPMs; the tone does not change when the engine is revved, only when the speed of the vehicle increases. Oh, it also doesn't make the noise when the car has been sitting for a while. As the car warms up, the noise gets louder.

My first thought was bearings in the differential, and/or crappy fluid. The fluid WAS crappy, and I changed it, but upon inspection there was nothing wrong with the bearings. My second guess was wheel bearings but, again, inspection reveals nothing of note.

Today, I wanted to check some things again, so I jacked the rear end of the car up and spun the wheels by hand whilst the transmission was in neutral. No sounds, no resistance, I couldn't find anything wrong. Drive shaft u-joints seem to be fine, pinion bearings are solid. No noise at all from the wheels spinning. I was getting a little bit desperate at figuring it out, so I started the car. My plan was to throw it in drive with the rear wheels off the ground, crawl underneath and try to listen for any errant noises. Yes, I know that's a terrible idea, but bear with me because I didn't actually do it.

But I started the Jeep and, while it was still in neutral, I noticed this:


Now, I'm no scientist, but if I remember high school auto shop right, the wheels aren't supposed to spin while the car is in neutral. Granted, it wasn't a hard spin -- I could stop it by expressing pressure with my non-dominant pinkie, even spin it backwards... and I imagine that it wouldn't be able to move the weight of the car... but as soon as I'd let go, yonder wheel (and associated drive shaft) would slowly start picking up momentum again.

While this does not get me any significantly closer to figuring out the location of the noise (after all, even with the wheels spinning I couldn't hear anything funky), it did leave me wondering whether this sort of thing is supposed to happen (which I imagine is a firm, er, "NO"), and if anybody else had any idea what might be going weird on this thing to either cause such behavior or cause my rear end noise.

Any ideas, o' gurus of XJ?

aa7kn

well I know the tires should not move in Nuetral. maybe it is a tranny problem. seems like thye linkage ot something is keeping pressure on the output of the tranny. but not much as you can stop it by hand. really a strange problem. keep us posted if you find out the problem.

Turbo X_J

"I was getting a little bit desperate at figuring it out"

Sounds like it, have you tried turning up the volume on the radio?

Derision

That was actually my first course of action. I still have the stock speakers, though, so they don't drown out much of anything.

It's a very odd one, and something I've never encountered before. The transmission, though, works great. Shifts beautifully, no slippage, no noise, so it's a bit unnerving to see it do something weird like that. I'm going to try taking it to a shop, see if they can put it on a lift and then try it again, see if it still does it and if I can figure out why, having a better look at the thing's soft white underbelly.

Radi

tires turning a bit in neutral while up in the air isn't uncommon. Seems like it should be something ominous but it isn't. There's nothing wrong with it.

How's your transfer case fluid? Does the noise change in 4WD?

Hamster

[QUOTE=Radi;1886511]tires turning a bit in neutral while up in the air isn't uncommon. Seems like it should be something ominous but it isn't. There's nothing wrong with it.QUOTE]

^^This. It's a common occurance at the shop where I work. They should not spin in Park but in Neutral, sometimes they do and sometimes they don't.

Cherockee

Check the output shaft of your t-case. I'm thinking the bearing on the slip yoke is bad or possibly the u-joints on the rear driveshaft and then maybe the pinion yoke of the rear differential.

Derision

The saga continues!

This droning nonsense has been going on now for nearly 2000 miles. It hasn't gotten any better and it hasn't gotten any worse, but it's definitely noticeable. I've gone through some preposterous measures to track it down, including pulling the carpet up and sticking my head through a hole in the floor while someone else drove so I could actually look at my rear differential -- but I still can't hear it outside of the car.

Whatever is making the noise is transferring this vibration/noise through the drive train to the leaf springs and into the chassis. This I'm fairly sure of because it sounds like it's in the rear, and loudest in the rear driver's side -- but then my passenger side leaf spring is saggy, so it doesn't transfer that resonance as well. I have, at some point, suspected everything from the wheel bearings to the drive shafts, but nothing seems to pan out.

I've been driving it hoping that, maybe, something will break a bit more and it'll make more noise, or start clattering or something, so I can track down the origin. But, as said... after 2000 miles, it hasn't gotten better and it hasn't gotten worse.

So I finally broke down and brought it into a shop (Pep Boys, mostly because it's nearby and I can walk home if need be) a few days ago, and had one of them check it out. The guy said that it was a wheel bearing, but I didn't have the time to fix it then so I scheduled an appointment for the next day to bring it in.

When I brought it in the next day, I told the new person that was going to be working on it what to get the noise... get to 35 miles per hour and give it light gas, and you can't miss it. The dude hopped in, drove around the parking lot, hopped out and announced to me that the rear differential was shot and that I'd have to replace the whole rear end. Quoted me something like $4800 to do it.

Wanting a second opinion on price, I called another place, which specializes in transmissions and whatnot. I told the guy what Pep Boys had quoted me, and I think he about spit his coffee across the desk. Told me to bring it in and they'd have a look.

So I did. Four guys pored over the Jeep for about two hours. Jacked it off the ground, one guy would rev it up while the other guy listened to everything with a screwdriver to his ear, and then they'd alternate, then they'd drive it around, then they'd do it all again. After a few hours, the lead guy came in and said that he didn't hear anything wrong with the differential or wheel bearings, and that he was pretty sure that the sound was coming from the transfer case. I'd never checked the fluid on the transfer case, so we opened it up and there was a bit in there, but it definitely wasn't full. I mean, if I stuck my finger in the fill hole I could just barely reach the top level of fluid.

So we put more fluid in. He drove it around and said that he thought it had quieted it down a bit, but I didn't notice any difference. The shop's opinion was to drive it and, if it gets any worse, then rebuild the transfer case.

I'm getting some serious agita here trying to figure out what it is. Considering the amount that I drive (I've driven 11,000 miles in the four months I've had it) a catastrophic failure would be somewhat... er... catastrophic.

So I suppose my question would be... would a transfer case be capable of making a droning noise that sounds like it's coming from the rear end? I would think the transfer case might clank or thonk or whatever, but I never attributed a drone to it.

Thoughts?

Cherockee

Sure it can make that noise. It has several bearings in it that can go bad. Relatively speaking, replacing the transfer case can be fairly cheap if you can find a good one at the junkyard.

Derision

Yeah, it was a huge relief when they told me it was the transfer case and not the rear end. To do a rebuild on the t-case, they gave me an estimate of $500... which is infinitely better than the $4800 that Pep Boys was trying to foist on me.

I guess I'm mostly just paranoid that maybe Pep Boys was right and it is the rear. I don't hear any noise from the transfer case but, again, whatever noise it is, is travelling down my driveline and appearing where it attaches in the rear, like a string between two cans.

Here's question 2, then... what precisely happens when the transfer case DOES completely crap out?

jebmccall

several different things can happen, they can explode, they can lock up a bearing and the shafts wont move, make really bad clanking noises, etc. might try removing the rear drive shaft and greasing the slip joint.

Cherockee

And actaully a good thing to do first,regardless, is to replace both U-joints on the rear driveshaft. Pretty cheap, are normal wear items, and can usually be done by the backyard mechanic with common hand tools. And even if it doens't cure your trouble you'll have peace of mind that the u-joints are good for many thousands of miles to come.

Derision

I have FINALLY gotten a proper diagnosis on this nonsense.

As mentioned above, the first diagnosis from Pep Boys was bad wheel bearings, which was then changed the next day to the rear end being shot. The next shop that looked at it decided that it was the transfer case making noise, though I was a little uncomfortable with that opinion because I'm sitting on the transfer case and don't hear anything.

So I took it somewhere else. The guy there informed me that it was the pinion bearings, that it was very common and that he had four other Cherokees in the lot that he was doing the exact same thing to. He quoted me a price, I was about to fill out the paperwork when he explained that, because he orders to parts directly from Jeep and they apparently only deliver via dog sled or something, that I'd have to leave the thing there for like two weeks. Which doesn't work well for me because, er, I have to get to work.

So I was going to be in Maryland for a few days, and I wouldn't need the Jeep, so I called a station down where I'd be staying. The guy there told me he could do the work, and that it wouldn't be weeks and weeks. So I took it in and dropped it off. A few hours later, I got a call to come down and see what they found.

WHEEL BEARINGS.

That's all it was. The wheels bearings were bad. One of them disintegrated upon removal. And whereas Pep Boys estimated $230 per wheel, this place replaced both rear wheel bearings, both axle seals and changed the differential fluid for $250.

Noise equals... gone!

Er, mostly. Like 90% gone. There is a very, very faint hum from the rear end, and the guy told me that it was the carrier bearings. But, he said, he had the rear end apart and everything is wearing as it is supposed to, and there's no play or any issues he can see, and so not to worry about it. His recommendation was to turn the radio up, because the rear end could probably do another 100,000 miles like that, and that the cost it would take to rebuild the thing would probably just be easier spent buying another Jeep or another rear end to swap in.

So there it is. Two months worth of noise, and 3,000 miles worth of worried driving and five contradictory diagnoses, and the actual problem was 90% wheel bearings and 10% carrier bearings. And 0% transfer case or pinion bearings.

I can finally sleep again.

Bbasso

Good to hear, I too have been wondering about a front end noise. I've been thinking wheel bearings and wanted to see what happened with yours first lol

Crazy Amos

Thank you OP for keeping this thread updated! I have read thread after thread where people ask questions, they get opinions and then after they fix it, they never up date the thread to let everyone else know what the fix was. So again, THANK YOU.

I have the same noise as you did. Im not sure as to what it is quite yet but I am trying to locate it. I do think mine is in the transfer case output though.....right now anyway.

The PO drove on completely worn out shocks for a looooong time and my susupension and drivetrain absorbed all of the impacts for so long that its hard to tell where its coming from for sure.