Please help diagnose drivetrain noise.

2000/auto/242 w/ 127k miles. The noise sounds like a bad bearing. High pitched squeal/scaping sound that started recently, and I think is getting worse. There are no vibes assosiated with the noise. I thought maybe a vacume leak, but couldn't find one. So here's the deal. It is tied to vehicle speed, not engine speed. Does not change when tranny shifts. Louder the faster I go. Does not change between 2 or 4 wheel drive. When on the gas it is loudest, when I get off the throttle all the way, it is the same but quieter. I can get the throttle to match the speeds and make the noise stop totally. Between drive and coast. I am sure it is in front of me and not coming from the rear. I think it is coming from my TC

Recently regeared both ends, but it didn't make noise before, and I have about 700 miles on them. Good patterns and BL in spec. Put in an OX last weekend so I had to adjust my rear backlash. Left it at .009. I really don't think it is my diffs/gears. Yukon gears and master instal kit w/ Timken bearings. Changed oil at 500 miles and they looked great.

My pinion angles sucked, but they are fixed now. Shims and adjustable CAs. CVs front and rear. I have vibes at 60-70mph, but don't think it is angles. I am taking both shafts in next week to replace joints and balance them.

I also put on a TnT belly skid. Had a 1" drop before. The skid rasied my TC 1" above stock. The linkage is a little off. That would change my driveshaft angles a bit. Don't know if that has anything to do with it.

So I regeared, but they sounded good. I have had locker problems and haven't really drove the XJ for the last month. It doesn't sound like gears or like it is comming from the diffs. Even though that would be an obvious answer. I think it is my TC, but don't know what. I had bad front vibes till I fixed it. Maybe it toasted my bearings? I am at a loss. I have done so much work lately, don't know where to start. Vehicle speed noises are limited. Can't be a wheel bearing cause it changes between coast and drive instead of being steady. My next move is to take off each drive shaft and see it I can at least determine front or rear. So how about it, any guesses??? Thanks

I'd bet on rear driveshaft angles or rear diff. Unibodies are great for making noise sound like it's coming from the other end of the vehicle. You described a torque specific noise/ speed related, so that's where I'd look.

Front hub

Dirt Surfer said:

I can get the throttle to match the speeds and make the noise stop totally. Between drive and coast.

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Front hubs don't react to throttle setting.

Well 127k and if they are the OEM hubs, it wouldn't hurt to swap in some hubs/axles to at least rule it out.

JJacobs said:

I'd bet on rear driveshaft angles or rear diff. Unibodies are great for making noise sound like it's coming from the other end of the vehicle. You described a torque specific noise/ speed related, so that's where I'd look.

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You have no idea how bad I do not even want to consider the rear diff!!! I'm on my 3rd locker. I don't think that is it, but even still...

It wasn't making noise before. It could be gears, or bearings. I put the OX in to replace carrier and EZ locker. My pinion uses shims. My new seal was leaking, replaced it while I had my axle out. So...Replaced pinion seal. Torqued nut back down to 250lbs. Spun good, just a tiny bit more drag, and I mean tiny. Figured it was the new seal. Installed locker, ring gear locktighted and torqued to spec. BL was way off. Adjusted w/ setup bearings. Pressed on good ones, had to readjust once. Got it to .009 and called it good. We had to pound in the carrier originally on the first setup. It came out real easy after it broke in. I could pop it in and out, but this time on final install I added .007 for preload. Needed a rubber mallet, but it was not even as tight as before. Just snug

So if it is the diff, I don't know what it could be. Since I had set pinion depth before, and the gears were broke in, I didn't bother running a pattern. I had .008 for BL when I pulled out the old carrier. (I did measure) So I only changed BL by .001. Maybe I preloaded the carrier bearings too much? Should I have not added more shim to tighten it up?

Sunday I can work on it some more. If I pull the rear shaft, and there is no noise, would that be conclusive that it is my rear diff?

ChuckD said:

Front hub

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x2
you describe exaclty symptoms ive had with OEM hubs.

Sounds like the center bearing in the drive shaft, but could also be a u-joint.
Hey, it just might be a muffler bearing.

JJacobs said:

Front hubs don't react to throttle setting.

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maybe he thinks the noise goes away because the tires/road noise/motor drowns it out.

Honest, I'm not arguing. I asked for input... How could it possibly be the front hub??? I did once consider pass side, but like I said, I can make it stop if I hold the throttle in the right place. I just had 2 bad bearing on my 2005 Subaru replaced, So I have dealt with that recently. Just for argument though, they are original bearings. In the last 3 months I put 1.25 spacers on to widen my front. I had to replace my disks. I had to use a press to get them off my bearings. Scared the crap out of me! Went off like a gun shot. That is kind of expensive just to replace uni's for the hell of it.


Also, I know it isn't muffler bearings cause I just had those replaced! HaHa

skyjackedxj96 said:

maybe he thinks the noise goes away because the tires/road noise/motor drowns it out.

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No, that's not it. It is plain as day. As soon as I get off the gas, the noise stutters and quiets down. Like I said, if I keep pressing down on the gas from coast, I can get the noise to stop totally. That is why I can't see it being a wheel bearing. The only thing effected by vehicle speed in drive or coast would be everything after the tranny. I'm not an expert though, that is why I am asking for help. So thank you all for your input.

I guarantee the noise will go away without the rear driveshaft. Whether it's diff or driveline is hard to say.. but.. I have heard similar torque related buzzing noises caused by driveshaft angles. Throw a bunch of weight in the back and see what the noise does.

JJacobs said:

I guarantee the noise will go away without the rear driveshaft. Whether it's diff or driveline is hard to say.. but.. I have heard similar torque related buzzing noises caused by driveshaft angles. Throw a bunch of weight in the back and see what the noise does.

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OK, you made your call. I have a bunch of weight at work, so I can do that in the morning on the way home. If I pull my rear DS, and the noise stops, how am I going to determine what it is from there? Would anyone sugest putting my XJ on blocks and putting it in drive to drive the wheels? If it was the diff, would I be able to hear it outside the vehicle? Would there be enough load with the wheels turning in air?

If the weight changes the noise, it's the driveshaft/ driveshaft angle. If it stays the same it's in the diff. Spinning up the Jeep on jackstands should also tell you if it's the diff, but you may not hear the noise if it's driveshaft.

Dirt Surfer said:

Honest, I'm not arguing. I asked for input... How could it possibly be the front hub??? I did once consider pass side, but like I said, I can make it stop if I hold the throttle in the right place. I just had 2 bad bearing on my 2005 Subaru replaced, So I have dealt with that recently. Just for argument though, they are original bearings. In the last 3 months I put 1.25 spacers on to widen my front. I had to replace my disks. I had to use a press to get them off my bearings. Scared the crap out of me! Went off like a gun shot. That is kind of expensive just to replace uni's for the hell of it.


Also, I know it isn't muffler bearings cause I just had those replaced! HaHa

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Don't you have spares? If not I recomend getting them anyway. Also why don't you see if any of your Chapter buddies could hook you up. BTW, junk yards have tons of them and having spacers and wheels that do not have the stock backspacing can do a number on the hubs.

www.car-parts.com

Because you said you thought the noise was coming from up front and one off my XJ's squealed like a pig until I replaced the culprit hub.

Well still clueless. Reving engine in park, no noise. Took off rear driveshaft, went for spin. Noise still there. Although a little harder to hear with TC noise. Jacked up rear axle, wheels spin nicely. No slop or anything strange w/ pinion. Took off front shaft, put TC in neutral. Both ouputs seem to spin freely w/ nothing strange. Jacked up front, both wheels spin free and quiet. Nothing strange w/ front pinion. Put spare/different shaft on the rear, go for drive. Same noise, no change. Still responding the same to throttle inputs. I am somewhat sure it is comming from front, but hard to pin point. WTF! Any ideas???

I forgot to put it on blocks and run it in drive. It is late now. I will do that tomorrow when I get up.

Anyone??? What else could be throttle related. I guess I'll just wait for something to blow up.

:repair: i didnt read all your posts in detail, but i had a noise on my tj and it was the front drivshaft ujoint. it looked good , but when i took it out it was all rust inside.... just so you know

Right now I am running my spare shaft in back. I still have the noise though. I sent my F/R shaft to be balanced and new joints put in. The CVs are bad and need new centering kits. When I get them back I at least know it's not them. Hopfully that will rid me of my vibes I have which are unrelated to the noise.

Dirt Surfer said:

Right now I am running my spare shaft in back. I still have the noise though. I sent my F/R shaft to be balanced and new joints put in. The CVs are bad and need new centering kits. When I get them back I at least know it's not them. Hopfully that will rid me of my vibes I have which are unrelated to the noise.

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Have you broken an axle in the rear? Have you checked to make sure that the yoke is true? double check the runout on the rear pinion yoke. remove the yoke and check the pinion shaft for runout. Ive been chasing a similar problem for 3 months and have finally worked it down to the rear end. Its probably NOT the t-case, if youve rebalanced your DS's a few times like I have and still have the problem then its most likely something else. start at the axle bearings and start checking the moving parts all the way to the t-case. I bet you stop at the pinion yoke.

Thats my $.02

Aaron