2004 GT when I accelerate I get a vibration in my seat, steering wheel and sort of fills the car...but its worst on drive with o/d off...withdrivetrain 1:1. Its worst at 30 mph but is there at 50 too. Its not a shake like bad balance and I have new tires...it is there driving straight lines or turning. I'm wondering about drive shaft...tranny....tranny mount. I need to have a vibration study done I guess, but wondering if there is any one out there that has had thisb sort of issue crop up.