95 SC300 w/90k. A distinct vibration felt below the passenger compartment and rear of car beginning at 65, worst at 75, and tapering off but still noticeable from 80+. Doesn't matter if under power or not. In addition to vibration, car sounds like it has truck tires on it when vibration starts. Absolutely no vibration or shake in sterring wheel. I have replaced tires with new Michelin's, centering rings added to after market wheels (even changed out wheels to eliminate that as cause) - no change. New drive shaft installed - no change. Bell Lexus in Phx had car for two weeks and it was a nightmare; they didn't have a clue how to fix it. I'm reading similar, but not the exact same problem, and comments about CV joints or transmission mounts, which Lexus said they checked and were not the cause. Pretty frustrating when the manufacturer can't even fix the problem. If anyone has experienced this vibration (without front end for streering vibration) and knows the fix, I would be grateful. Hate to give up car because it rides like a Lexus up to 60 mph, but I can't "live" with the problem as some have suggested. Thanks.