spitanddirt

Alright, normally I know exactly what a bad wheel bearing sounds like but this is driving me mad. At first I thought that my tires were wearing out and I have replaced all four with new Michelin's. A while back my center carrier bearing on my prop shaft started sounding like jingle bells under the car and so I had it replaced.

Now, before I go and spend almost $300 on new bearings for the car from Blauparts, I want some input and opinions. I have almost 175,000 miles on the car. The alignment is presumed to be good since the last time I had it done. The car tracks straight and the old tires had NO evidence of irregular wear or cupping.

The problem I have now is that my steering wheel will sometimes vibrate back and forth indicating that my tires may be out of balance, but other times the steering wheel doesn't vibrate at all. I've had my tires rebalanced twice, I've even tried two different shops. I've tried new pavement, old pavement, concrete, asphalt, etc. In addition to the steering wheel vibration, I get this low rumble right at around 40-45 mph. That's when it's most intense. From about 5-20 mph, I get what sounds like a "wah wah wah wah" cycling from the drivetrain.

I've replaced all driveline fluids, I have no leaks under the car. All brake rotors were replaced and calipers were rebuilt about 20,000 miles ago.

All CV shafts appear to be in good condition and I've never heard a single clicking sound on turns. All front suspension arms have been replaced and it doesn't appear that any of them have any play, I've checked.

Let's not forget that I've checked for top and bottom, front to back free play of each wheel. None that can be detected even if I use a pry bar to lift the wheel up and down.

Which brings me to why I'm so frustrated. I thought I have a car that's supposed to be ridiculously quiet traveling down the road but what I have is a car that resonates at odd frequencies on the highway.

The last check I've done is to jack each wheel about an inch off the ground, lay on my side under the car, and listen with a mechanics stethoscope on the backside of each wheel bearing while I spin the wheel by hand. From my experience, I shouldn't be able to hear anything from a wheel bearing. In this case 3 out of the 4 wheel bearings has a subtle "clink clink clink" when I spin the wheel. This is only reason I'm starting to suspect that my bearings have reached the end of their service life. Since I can't listen to each of the bearings as they under load, I'm forced to make a judgement call. Just to rule it out, I can hear the subtle dragging of the brake pad against the rotor. It's not anything I would call excessive.

If anyone has any personal experience with any vibration issues, please enlighten me. Above all else, I hate(and can't afford) to throw money at problems to which I'm just guessing. I've googled Audi wheel bearings and from everything I've researched, apparently no one tends to have problems with their wheel bearings on their A8's. Am I missing anything?

silverd2

I've only found 2 things that will pulsate through a steering wheel...and both can be more prevalent at certain speeds >>

Maybe not either one of these, but for all it's worth:

Outer front CV...even still sealed (and feeling OK when checking) can possibly wear grooves (***** against races), esp at straight on position where it rides 99% of the time.

Or a warped (bent) wheel.

I've found warped wheels before, by jacking up that wheel and placing a solid reference "object" on the ground and check gap as I slowly spin the wheel.

As for listening to each wheel with stethoscope: since all the parts are directly connected mechanically and all transmit vibration, you could be hearing normal CV noise (*****/rollers pulsating back & forth normally) or even the helical differential gear teeth meeting normally.

Bad bearings should be turning/load (and unload) sensitive...almost always.

TSHong

I also agree with silverd2, I would suspect a cv axle instead of a bearing. Bearings make noise but rarely vibrate. A loose cv joint has a classic symptom of vibration at certain times, usually under acceleration and deceleration.

Adjuster

My guess is a half shaft problem too. Have any been rebuilt? Or are the boots still OEM stock, or new?

It's also possible the driveline could be 180 out, I've seen it where if you don't put them in exactly how they came apart, it can affect the balance, and that vibration can show up in weird places, not just the center tunnel area.

Any failed wheel bearings I've ever had, or worked with have a pitch that changes with load, speed and side loads. (IE: Going straight, turning, or fast or slow.) The pitch change when turning on one vehicle was so "interesting" you could nearly play a song while driving the car, and move around side to side in the lane loading and unloading the failed bearings.

Good luck either way, chasing down these things on old cars can drive you crazy.