Strange noise - solved
12-06-2011, 04:47 PM
#1
Head Cat Herder
Thread Starter
Strange noise - solved
I had been experiencing a really annoying noise in y '00 A6 Avant for a while now. Being all too familiar with wheel bearing noises, and tire noise etc, this sounded like a wheel bearing to me.
So I brought it to my trusted local shop, where one of the owners actually looked at the car. He said that all 4 wheels, axles, everything was fine. this is all good, except it doesn't solve the noise, which was still there. One thing he did say was, he'd seen noises like this on other vehicles, namely Jeeps, when the driveshaft had gotten bent. Instantly I thought back to last fall, when I had the run in with the big rock - Which not only crushed the trans pan, and broke the exhaust, but it bent the driveshaft.
I determined that it was bent a few mm in the rear section, and as the speeds increased, the vibrations were running through the rear diff housing directly to the body.
One tip that the owner of the shop gave me was crazy enough that it just might have worked. Since the driveshaft has flexible joints on the ends, the bend itself isn't causing the problem, it's that the shaft is out of balance. So, how to balance it? well, the tip is, use a hose clamp. The "big" side of the clamp is heavy enough in many cases to balance a bent shaft I was told.
So, after determining where the high and low points on the shaft are, I put the heavy part of the hose clamp on the low side, as close to the middle of the shaft as possible.
Amazingly enough, 1 $.50 hose clamp balanced the bent driveshaft enough that the horrible noise is gone. I'm still going to look for a used driveshaft, but at least the car is quiet now.
So I brought it to my trusted local shop, where one of the owners actually looked at the car. He said that all 4 wheels, axles, everything was fine. this is all good, except it doesn't solve the noise, which was still there. One thing he did say was, he'd seen noises like this on other vehicles, namely Jeeps, when the driveshaft had gotten bent. Instantly I thought back to last fall, when I had the run in with the big rock - Which not only crushed the trans pan, and broke the exhaust, but it bent the driveshaft.
I determined that it was bent a few mm in the rear section, and as the speeds increased, the vibrations were running through the rear diff housing directly to the body.
One tip that the owner of the shop gave me was crazy enough that it just might have worked. Since the driveshaft has flexible joints on the ends, the bend itself isn't causing the problem, it's that the shaft is out of balance. So, how to balance it? well, the tip is, use a hose clamp. The "big" side of the clamp is heavy enough in many cases to balance a bent shaft I was told.
So, after determining where the high and low points on the shaft are, I put the heavy part of the hose clamp on the low side, as close to the middle of the shaft as possible.
Amazingly enough, 1 $.50 hose clamp balanced the bent driveshaft enough that the horrible noise is gone. I'm still going to look for a used driveshaft, but at least the car is quiet now.
12-06-2011, 04:56 PM
#2
AudiWorld Super User
Great find Kris, thanks for sharing it.
Reminds me of the occasional noisy HVAC blower wheels I have to balance with clips in the vanes, it makes sense.
Last edited by jcman; 12-06-2011 at 04:58 PM.
12-07-2011, 06:45 AM
#4
Wow, that could have cost a fortune in replaced parts if he didn't mention that. This is a perfect thread for people who start replacing parts without proper diagnosis - including myself at times.
You could have spent hundreds on wheel bearings, breaks, you name it. You spent $1.50. The diagnosis was time well spent!
You could have spent hundreds on wheel bearings, breaks, you name it. You spent $1.50. The diagnosis was time well spent!
12-07-2011, 11:30 AM
#6
Head Cat Herder
Thread Starter
Thanks! Yeah, I was pretty happy to have a simple fix on this one. I'm sure I'll end up replacing the driveshaft at some point, if a used one comes my way, but at least I didn't spend thousands of dollars trying to replace things that didn't need to be replaced.
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12-07-2011, 11:32 AM
#8
Head Cat Herder
Thread Starter
I generally do, this one was driving me batty though. Luckily, the guys at the shop also believe in diag, and are really good with the stethoscope, which reminds me, I need to get one.
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