If you're not sure of the source I'd say to start off by checking the right hand side wheel bearings (And even though it sounds silly the wheel nuts too) and work your way in towards the diff, once you have it up in the air hopefully whatever is wrong should make itself apparent. Also check the height of the vehicle both sides, make sure it's the same. Apart from that I can't think of anything else but I'm fairly new to P6's so hopefully one of the old hands will take it from here.......
"Kate. It's short for Bob"
1972 2000SC Davos White with Toledo interior.
1986 SD1 VandenPlas EFI Silverleaf with flint interior.
1986 SD1 2300 in Moonraker Blue, awaiting recommission. * EDIT Now undergoing recommission*