Grinding noise from rear
 

Hi,

Just noticed my 2001 2.8QS (103k) making an odd grating grinding noise when pulling away. Doesn't happen all the time but does seem to happen more often when going round a bend. Sounds like a piece of metal dragging against the road but checked and can't see anything obvious. Pretty sure it's coming from the rear. Could it be rear dif?

Thanks

Or a seized rear calliper? They are prone to that

I'd agree with that sounds like a seized rear caliper, which would also affect your handbrake operation too on at least the one side. I've just replaced the OSR one on my D2 with a new caliper +++

Oddly, so did I, well a bit earlier this year. New NSR caliper, not exactly cheap!

Sorry maybe I didnt describe the noise well enough. I have had a stuck caliper before and I take it the noise your talking about is the worn break pad (down to metal) grinding against disc? I have checked both calipers afer a journey and they are pretty cool to the touch.

The noise is more like a very loud mechanical clicking sound, similar to what I'd imagine two cogs slipping would sound like coming from the rear area. Any ideas? is the rear dif a weak link?

I have never heard of a read diff going, either on this forum, or the US forums (quattroworld, audiworld). So I guess they are quite strong.
You may want to check oil level in the rear diff, I believe it should be level with with bottom of the oil plug hole.

Also, non worn brake pads will make a noise for the first few yards if the car is kept outside due to rusting on the disc, mine does every time it sits for a few days. Rear calipers are not seized.
Also, sometimes a slightly dented or lose gearbox heat shield may catch a drive shaft or wheel at full lock only and produce a metal scraping sound, if you have access to a lift may be worthwhile looking under the car to see if any moving parts touch anything at full lock.

Similar to you I have never heard of dif's going but everything currently seems to point to it...

I read on a US forum that you can test if its the dif by ever so slightly applying the handbreak which disengages the dif (or haldex?not sure) as your moving and this, for me, kills 90% of the noise.

Im pretty sure its not the breaks as I have just recently had new calipers, disks and pads. They breaks arent rubbing as they are cool to touch after most journeys & I have heard dodgy breaks many a time.

Its more of a fast 'clack clack clack' noise, similar to a draw bridge being lowered for want a better description. Only happens when accelerating round a corner.

I have it booked into autohaus in Edinbugrh on wednesday to get it checked over.

CV joint?

If the noise is more of a tinny clatter, it may just be loose brake pads. I wouldn't describe that as a "clogs slipping" type of sound though; more like an exhaust rattle.

I had the loose rear pads noise once. The pad clips hadn't been correctly refitted so the pads were clattering against the discs. Took a while to realise what it was. It sounded more like something loose underneath the car. If it's pad rattle though, you can usually diagnose it by lightly braking while driving to stop the rattling.

Its less of a tiny clatter and more of heavy machine gun, I was shocked how loud it was when I opened the windows, just shows how good the sound insulation is in an A8!

Will check if brakes kill the noise but i dont think they do, bar using the handbreak ever so slightly. That definately works. So is it true that with the handbreak applied, even slightly, a quatrro becomes a FWD?