I get what appears to be a driveline vibration at about 100+ MPH and it get's worse and more violent the faster I go. Anything below 100 is perfectly smooth. It doesn't have anything to do with RPM and I have tried different gears including neutral and coasting and there is no change. I recently had my rear end gone through and axles inspected so I think I can rule that out. I have a Drive Shaft Shop 1 piece aluminum shaft that I have tried rotating 180 degrees and it may have made a slight difference but nothing big. I then took the driveshaft to my local driveline shop and they balanced the shaft. For wheels on the car I have American muscle 2010 GT500 style wheels with Michelin Pilot Super Sport tires and I have had the wheels checked for true and a trusted shop road force balanced them and didn't find anything of concern. The vibration gets worse with speed and has no effect on the steering wheel. The whole car seems to be affected and can be seen by vibrations in the dash or rear view mirror. It stays the same wether I'm accelerating or coasting anywhere above 100 or so MPH.