I have a stock 2001 XJ, with 70,000 miles on the clock. Lately, a noise/vibration from the undercarriage has developed, which has got progressively worse over the last month or so. It's a sort of metallic churning/droning sound, which is louder when the car's coasting than when it's under power. It's as though everything down there needs a lot of grease. At first it seemed to come from the front end, so I removed the front driveshaft to see if things would run smoother - no difference.
Now, after a long trip, the noise seems to be more from the back axle, and there's also an occasional 'clonk' when pulling off from a stop. There's also a bit of vibration in the steering. I had the shock absorbers checked - they are worn, and so are the tires - about 3mm tread left. There is also some uneven tire wear due to the worn shocks. Could that cause the noise? Sounds more like wheel bearings/diff noise to me. I'd really appreciate any advice on this, as it's a difficult thing to diagnose.

 

Could be your gears grinding..take your diff cover off and inspect..

 

Really sounds like a U joint.

The gap between the cap and rest of the joint could be causing the clunk, too, as there are needle bearings in there that discintigrate and leave space.

 

Did you check the rear drive shaft? What you are describing could be a rear drive shaft u-joint. Check the diff fluid levels. Check the rear brakes. Basically check everything you can possibly check that has anything to do with the drive train.

 

That clunk on acceleration would be your u joint most likely. I would start there and then check you diff. Inspect the ring gear and fill it full of fresh fluid and see what happens. If it ends up that there are serious problems with the diff, time for an upgrade. You never did state what rear axle you have but I'm going to guess Chrysler 8.25.

 

The rear axle's a Dana 35. I did change the oil about a year ago, but only by siphoning as much old oil out as I could, not draining it completely by removing the cover plate.

 

Fluid levels are definitely OK. With the rear brakes, what should I be looking for?

 

I had a similar problem on the rear axle(8.25) at first i thought it was the T-case, then my wheel bearings, then axles but after replacing the fluids and bearings,seals etc. Then finally just dropping the rear end i went to slide it out from underneath the jeep and the wheels would just lock up about every quater rotation,so guess it was my gears! I simply Replaced the entire rear end after that.

 

Check to make sure the brake shoes are in place and not floating around.

 

I have this noise as well, im currently inspecting the problem. I have so far ruled out the rear and front diff, flushed and inspected, shows no wear.

Does your E-brake work?, mine snapped and I have a feeling somethings churning around in the drums, or bad bearings...

too damn cold, dont have too much motivation to play with the rig right now.

 

Turdy5s like to eat pinion bearings in my experience but with only 70k thats surprising. The ones I have seen where the bad bearings show up is after 140k. (3 of the last 3 I've owned)

 

Get under and see if you pinion moves or where the driveshaft goes in the tcase it would a good idea to jack up back end spin tires and listen same with front if no problem sounds to me like a bearing

 

Wow! Thanks for the quick replies, guys. Seems like I've got my work cut out for me. One thing about spinning the rear wheels - when I tried that recently, I noticed they're very tight and difficult to turn. Is this normal? The front ones are pretty stiff, too, even with no front driveshaft.

 

Could just be brakes dragging maybe take of brakes and check its work but it will tell you and the back you can just back it off

 

Could be as simple as a rock in the rear brake drum, that is why you need to check everything out yourself.