Hi pete.
I had similar clunk on my q7. Clunk when pulling away( left right and straight line). Changed front drive shafts and front lower wishbone bushes and made no difference. Even took it to a guy who used to be an audi technician and he no idea what it might be, but said it could be something to do with the drivetrain. Changed the front and rear diff oil, still no difference. Put my gopro underneath the car in several places and the noise seemed to come from the transfer case. Changed the oil and added a bit of molyslip in and this cured it. Seems that the oil after 150000 miles wasn't lubricating the torson diff inside the transfer case.
Hope this helps
fraser
