Grinding noise

[alexi77]

So having attempted to change my sons rear discs and pads on his 2004 3.2 A3 quattro, gave up due to the carrier bolts being stupid tight.
The noise from the rear of the car is, a grinding scrape nose, speed related that sometimes disappears. ? I wondered if it was his worn discs however the pads seem fine , I tried rotating the wheels . 1 by 1 to replicate the noise without success. Is it likely to be the diff?, or cv joint. It is not very loud, however seems a bit disconcerting. Any suggestions on where to proceed would be appreciated.
Thanks in advance Alex.

 

[pluves1]

Could be any number of things including the haldex. Do you know if/when the oil was last changed?

 

[alexi77]

Yes I guessed as much, the car isn't with me at the moment, so i will need to check his service history.
Thanks Alex

 

[RustyBucket]

It's not as simple as a small stone that's embedded in a pad?

 

[alexi77]

HI, I have removed both sets of pads on the car to see if one had broken down, however they seem fine, only changing the discs as they have a lip on them.

 

[Bazzle]

Make sure you have the piston wind back tool as well
http://www.ebay.com.au/itm/Mercedes...331337?hash=item4643a0efc9:g:LfcAAOSw~bFWMhHf

 

[alexi77]

Yes I do thank you, I also relase the pressure via the bleed nipple so as not to damage the master cylinder.