clac clac clac clac

[Horst]

Hi folks,

for a few month I can hear an unusual noise fron the rear bottom of my 2000 A4 V6: At speeds between 20 and 25 mph and only when I am descelerating I can hear a sound that goes like clac clac clac clac. It is not loud enough to be heard when the radio is on. It can also not be heard when the car is accelerating or driving at a constant speed. The rythm of the clac clac clac seems to be linked to the speed.

The sound can also be heard rolling with the engine turned off in neutral.

First I believed it was the differential. I had it checked, but the mechanic said the differential is ok.

Then I had it checked again. This time with a stethoscope. The mechanic could not find wrong noises in the differential or the axle. But he located a strange noise in the centre bearing of the drive shaft. He recommended to change that bearing.

It turned out that the bearing could only be changed together with the driveshaft, which we did. Cost a fortune.

In the end, after a first testdrive the noise seemed to have disapeared. Now, a week later it has come back. Maybe not as strong as before, but it is there.

Strangely it seems to get worse on right turns, it seems to get better on left turns.

Any ideas????

Thanx

UPDATE:

Thanx for your replies. With regard to the RPO codes: The original Owner took the sticker off the door panel! But I still believe that I´ve got the LSD, ´cause most cars in the Euro-version came with that.

However - the fluid level is ok, as a matter of fact I had it changed. And the trans mount was checked, too.

BTW: My 2000 V6 has good the 1-piece driveshaft anyway.

I guess I will have a look at the torque arm next.

[ October 21, 2004, 03:43 AM: Message edited by: Horst ]

[Fredless]

make sure your tranny mount is ok and you have all the bolts tightened down right.

I had to change my tranny mount and didn't tighten one bolt all the way down and had the same problems as you.

Also check the torque arm.

[Denis]

Do you have LSD?

[FunkZ]

Most people put in a 1-piece shaft when that center bearing goes out, either steel or aluminum. You probably don't want to pay to replace it twice, but if you would need to, look into a 1-piece.

Check your RPO codes and see if you have a G80 (limited slip) as Denis suggested it could be the carrier, either due to wearing out or even just low oil level.

[Silver 99 Camaro]

If it's not a suspension problem get used to it. If you have posi, which you said you probably do, you have the Zexel Torsen unit (99 and later). Mine does the same thing. It clunks when downshifting, it clunks when getting back into the gas after a turn, it clunks when getting on and off the gas, and it sounds like a rythmic clunk clunk clunk sound when coasting at low speeds as you described. I've had the diff fluid changed twice over the life of the car, and had a transmission/gear specialty shop inspect it. They said those units develop play as they wear and make that noise since they don't use friction. The small gears get loose, and clunk when they engage/disengage. They told me mine was fine, that it won't break, but it would be noisy. Turn up the radio!

[Denis]

Yep, this is exactly the same story I got. I have the Y87 and I even took it to the guys at FBody Central to have them take a look and they said it's normal for the Z-T LSD. the folks at TA Creations also have a blurb on it here.

Torque sensing differentials make annoying nuisance noises.

[FunkZ]

I had noises like that coming from my rear before I swapped it. Same Zexel LSD, got it from SLP as a take-off, put about 70k miles on it. After disassembling the old rear I discovered this bearing was shot and the race was grooved like a record. The other side wasn't in much better shape either.

Picture

[Andy Belter]

I had a similar problem too. My occured after a diff. and gear swap and 2 hours on the highway. Basically what happened was when the guys installed my stuff the cover was not on tight enough and some fliud leaked out. Then I found out that the crush sleeve for the pinion had been over-tighted and crushed. This caused the axel bearings to be too tight making everything grind. In the end they had to cut the pinion out with a cutting torch becasue all the friction welded stuff together.
So checking out your bearings and stuff my not be a bad idea. My noise did go away after I had it installed correctly.
(Sorry this is so much reading.)