hello again, I have a 2003 RR autobiography, 100,000 miles; I had this problem a year or two ago and it eventually went away. Basically, I drive along, around 35-55 mph and intermittently, I hear an annoying groan from around the underneath of the offside passenger seat. It doesn't last long...merely 0.5 seconds then comes back again maybe a few seconds or minutes later. The noise is always in little bursts. I had someone change the rear diff oil which was pretty clean, but changed anyway....noise still there. It just comes and goes and is most noticeable when pottering along without foot hard down, but I think the car is under load when I hear the noise. It can best be described as a low groan.....or like going over mild rumble strips, but it is short lived as it comes in bursts. Its not buffeting from wind etc....def a kind of groan or booming noise, a bit like the base unit was up loud and it was vibrating really badly....it makes no difference if I switch to sport mode....or automatic. PLEASE help if you can, regards Simon