Hello all, my first post to these forums. I usually just get to lurk and benefit from your excellent knowledge, but this time I seem unable to help myself.

As the thread title says, I'm getting a sort of pulsating sound coming from the right rear. I'd say the best way to describe it is it sounds like braking with a severely warped rotor. In fact, back when it was very subtle, I was sure this was the cause and replaced both rear rotors when I changed the pads, but that didn't solve the problem. Here's a little more detail on the problem:

1) Noise gets louder when turning left and decreases when turning right
2) Frequency increases with speed.
3) Noise slightly gets louder when accelerating
4) Noise is present at all speeds, even when going really slow
5) When I have the rear jacked up and spin the right wheel I can feel a very slight patch of resistance at one spot and maybe a couple smaller spots. It's the same whether I block up the left or let it spin in the opposite direction. I can't feel this at all when spinning the left wheel.

The only possible causes I can think of besides the rotors, which we can now rule out, are:

1) Wheel/tire issues - I don't think it's this because the noise is present at such low speeds, like 5+ mph
2) Diff issues - it seems odd that diff issues would increase in volume when the weight shifts to the right, so it doesn't seem too likely
3) Bearing issues - The wheels are totally solid when jacked up. Not only that, it just doesn't seem to be that kind of squealing or grinding sound I would associate with a bearing so I think we can pretty well rule them out.
4) CV joint - It certainly seems like these could be an issue. I can get no clicking sounds whatsoever when accelerating, turning, braking, though and it sounds like you'll usually get that with an outer CV joint. At the same time, I think the outer CV would be more prone to change sound when weight shifts on the car. From what I've read on inner CV joints, it seems like the sounds of failure are at least somewhat similar, but they're never supposed to go out and all my boots are in excellent condition with no leakage. It seems weird for one to fail. The car only has 120k on it.

Is there any way to test if an inner CV is bad?

Are there any other possible causes I'm overlooking?

Thanks for your help!

 

it is a wheel bearing guarenteed. they can make all kinds of noises, my last one made a loud drone like a pulsating subwoofer. when you turn one direction and it gets louder, its a wheel bearing. theyre only like 70 bucks even at the dealer

 

usually with a CV its because the boot tears and the grease leaks out. You would most probably have noticed that when you had the car up. Do you have any kind of shake or vibration, or is it just the sound. My first thought is a balance issue.

or maybe your car just likes dubstep!

 

Wheel Bearing for sure! That's exactly what my wheel bearings sounded like when they went out (on two different occasions.) Replace it soon, as it will get louder!

 

I am pretty positive it's the wheel bearing.

 

^ I laughed.

I vote wheel bearing as well.

 

Another vote for the wheel bearing, just another one of the things that apparently go wrong with everyone's Audi. You might as well replace both of the rear bearings when you do it, as many others have recommended here. I had the rear driver's side go out, got it fixed and within a week or two, had the same damn noise coming from the rear passenger side!

 

Another +1 for wheel bearing. The all wheel drive is notorious for, as ImTheDevil once put it, "chewing through wheel bearings like popcorn." As said, bearings can be had on the cheap, and having inferred from your post that you are in fact running with Quattro, its a much easier job to replace than a wheel bearing for a FWD car so you're in luck there. As far as I've ever been told, it won't hurt to keep driving on it for a little while longer if you don't have the money/time right now, but replacing it sooner rather than later is definitely advised as it will do nothing but get louder and more annoying the longer you wait, as willie said.

Also, it definitely will be the right rear that you'll want to replace, not only because that's where you hear it, but because of the mechanics/physics of linear acceleration involved with turning. It softens up when you are leaning left because centripetal acceleration is shifting more force to the right side of the car (clearly demonstrated when you take a hard left turn and your coffee ends up in your passenger's lap), this linear acceleration applies more pressure to the right side, causing the sound to dim a little due to more resistance experienced by the bearing from the extra force. Likewise, it gets louder when leaning right because of the exact opposite; there is less force applied to the right side of the car resulting in less resistance experienced by the bearing, causing it to move easier and thus increase in volume. However, I should note that like brakes and lightbulbs and other symmetrical components of a car, you'd be more advised to change both rear bearings while you're at it because if the one has failed, the other is likely not far behind.

 

Wow, thanks for the quick replies!

Looks like I will be replacing both wheel bearings later this week. Thanks for steering me in the right direction.

kriptonik, I rarely laugh out loud at a post.

 

when your in there while your taking off the arm check for rips in boots and check the control arms they often fail and need new bushings =]