I've just been on a 300mile round trip to Devon & on the way down I could hear a funny noise but very hard to describe exactly. It kinda sounds like a faint squealing/clicking noise. When in drive you can hear it if you let off the accelerator pedal but as soon as you put your foot down even a little bit it goes away. Also when you can hear the noise if you put it in neutral while driving along it goes away then too. One other strange thing, on pull off there is a weird knocking but not every time, sounds like it's coming from the back but can't be sure. I had a horrible feeling the gearbox was about to give up but it felt perfectly fine all the way there & back. Could it be a drivetrain issue & is there any common problems with the Quattro system? The car in question is my S6 4.2V8 Tiptronic.