Three months ago I took delivery of a 2004 AWD S80 as replacement for my 2002 S80 that had transmission issue that Volvo couldn't fix. Since day 1 this car has had a vibration as if there was a tire out of round/balance only at speeds above 40 mph. The vehicle has 5000 miles on it and I have had four (4) sets of tires on this car.(stock Michelins, Kumoho's, Nokian WR's, and now Bridgestone's) The dealer agreed there was a vibration and so far has swapped out all of the rims with new ones. Vibration "seemed" to get better temporarily but has returned with a vengence. Third set of tires were Nokians WR's and last week in a desparation move replaced them with Turanza LS-H. Smoothest tire yet but alas vibation remains. Can feel it in your feet your seat, and in the wheel. Seats shake (even my children as me "why is the car shaking"?), sunvisor shakes, etc. New twist yesterday, crusing along at 70 when a loud "humming" noise started coming from rear of vehicle as is there was a large truck on the flank, (no truck). Became so loud that I had to pull off interstate because I was afraid someting serious was happening. As I stopped noise slowly wound down but not until after I stopped. Took 5-8 seconds after car was stopped to dissapear. Did not return when I started up again. I am getting to the point that I do not want to drive this car at all. Other than the vibration car is excellent. Comfortable, powerful, safe, beautiful, but the vibration is killing it. Any advice or insight would be GREATLy appreciated.