Noise from underneath rear of urS6 - anyone BTDT ?

[macspring]

When driving an auto urS6 slowing at about 10/15 mph on a trailing throttle there is a clucking noise from the rear of the car that is speed related.

As soon as one accelerates hard or gently it goes away. It is not always there, or there with the same intensity when one slows down again to replicate it and listen to it again. But there is definitely something amiss. Don’t feel it is brake related.

So when one slows the noise is there, but it is not always consistent in occurrence, but it is in sound when it does occur, but a definite cluck clunk that an uninterested passenger would hear without being prompted.

Please excuse the over detailed description.

While I think it is a CV joint, which I can deal with, I was wondering what are the symptoms of a faulty rear differential.

The noise is not a whine, but a mostly consistent clunk clunk in sympathy with the speed, (10/15mph), of the car, on a trailing throttle.

Any comments most welcome.

TIA.

[8690q]

Sounds like what I'm having going on with an 80 quattro avant just now.

See here http://www.s2forum.com/forum/showthread.php?t=56729

[macspring]

Bump.

[saltinot]

Have a look at the joints on the ends of the propshaft. The grease can dry and cake up in the joints oaver time. The one closest to the cats dries out due first to the heat it endures.

[macspring]

Tom, thanks for reply, forgot all about the propshaft.

[saltinot]

Yeah, the ole propshaft. It's worth a look and doesn't cost much to grease it up again. Worth doing even if it isn't the source of your noise. Cheap insurance.

[UrS4boy]

C4 UrS Propeller Shaft DIY info

From the UrS System and Chassis Map (click on the labels to go to the info you want, and then on the appropriate hyperlinks, as needed):

http://members.shaw.ca/speedtek/UrS%20chassis%20Map.html

[macspring]

Update and thread close out.

Thanks to Dave, Tom and 8690q for their replies.

Thanks to diagnosis by mcandmar, the problem is cured.

Very relieved, but super embarrassed.

The driver’s side rear wheel nuts were not fully tight, leaving just enough play for the wheel to "rattle" slightly when not under load at low speeds. "Tightened up” over 30mph and no noise.

Cheapest cure for once with these cars, if a little embarrassing.

[UrS4boy]

The driver’s side rear wheel nuts were not fully tight, leaving just enough play for the wheel to "rattle" slightly when not under load at low speeds. "Tightened up” over 30mph and no noise.

Don't feel too embarrassed. *Now* that you tell us the solution, I remember that an Audi friend came by the house a few years ago to have me help diagnose a clunking problem with his Audi 200 avant. Seemed to me to be related to the centre support bearing on the prop shaft (at least that was my diagnosis for him). Turns out, like your car, it was loose wheel nuts on one of the rear wheels.

*Next* time, I will offer that as the first check for such a noise.

Maybe.

If I remember.