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HELP - '99 XJ Buzz/Vibration/?

Hello all - it's been a while since I've poked my head in here, but I hope all is well with y'all.

Anyway, my '99 XJ (AW4 tranny) has developed a very strange buzz/vibration that I just can't figure out. When driving along, starting at ~40mph, this noise starts up. It's kind of like being inside a drum - more of a resonance than a sound.

As speed increases, the vibes will get stronger. But they don't seem to vary directly with the speed or engine RPM. Like I said, it's more of a resonance.

It does not vary with road surface, braking, payload, or maneuvers. Acceleration/deceleration makes no difference. I can put the tranny in neutral and coast and it makes no difference. In or out of 4wd makes no difference.

I've looked and listened all around the engine bay and found nothing that has the same frequency. The Jeep has to be in motion for it to happen.

If I run with the windows down, I hear nothing obvious. AC on/off makes no difference.

It's a very "heavy" buzz. Kinda like what you'd expect if the center guide bearing on a big truck's center driveshaft were going out and the truck was pulling a heavy load. Or possibly what you'd hear/feel if the AC compressor pulley bearing were going out.

The only feedback is a slight jingling of my keys in the ignition. If I put a finger on the ignition cylinder, I can feel a very faint vibe that matches the frequency of the overall drum sensation. But there's no feedback in the steering or anywhere else.

No work has been done on it, it's not had any accidents, nothing has changed.

I'm at wits end trying to figure it out. I'd welcome any suggestions.

Thanks to all!

Reply to
Clap Trap
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Good write up, hope you find the problem :) K.

Reply to
Kate

Check your exhaust pipe for contact on the body or crossmember, I had a similar issue with a '93 XJ.

Reply to
matt

Following up....

Found the problem. Front wheel bearing was shot. It was odd that there were no driving symptoms and no change in/out of 4wd. But it's fixed now and quiet as ever.

-clappie

Reply to
Clap Trap

Thanks for the follow-up. Glad you found the problem before it got worse.

You don't get driving symptoms from a failing bearing till you see the wheel bounce off into the distance. :/ The amount of wear that can make noise is no where near the amount you can feel simply by rocking the wheel. Guess it's similar to the squeaky idler pulley, but at least there you can get a stethoscope on it.

Reply to
DougW

Just a comment for future reference but sometimes you can diagnose a wheel bearing problem by noting whether the noise changes in turns. Turn left and the right side bearings get loaded a little more, turn right and the left side bearings do, and the changing loading may mean that the noise or vibration changes.

Reply to
J. Clarke

Another give away is your brake pedal. If your brake pedal is lower on the first pump after taking a corner, your wheel bearings are fried. That is how we figured out ours was gone. Ours didn't make noise.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

Not a bad check. Worth noting for the next time someone asks.

interesting ideas. I'd imagine if the bearings were out enough to walk the pads back that you could almost feel the bearing move by rocking the tire or hear it with a stethoscope.

I've had folks say that dragging the brake will make the noise stop for bad bearings, but that also stops noise from the whole drivetrain. Especially CV/UV joint noise by loading the joint up.

Reply to
DougW

One bad thing about those flat bearings is the wheel doesn't rock when they get loose like tapered bearings do, it just slides in and out.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:
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Reply to
Mike Romain

This one gave no symptoms other than noise. No change during braking, cornering, 4wd, or anything else.

Sometimes you can also tell a bad wheel bearing by going over "dippity-dos." You know - those times when you top a narrow hill and your stomach flies up. When you do that, you take load off the wheels and the sound can change. But that didn't work this time either.

The bearing was actually found by accident. I knew the axle u-joint needed replacement since it "hopped" in tight parking lot maneuvers. The bearing was discovered when replacing the u-joint.

Reply to
Clap Trap

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