Pontiac sunfire 2000 shake when driven certain speed
This car has an issue that I cant sort out. We have new tires, which we had ballances 3 times, had a front end allignment, and we even went as far as to borrow our neighbors wheels to do a test. When you reach the speed of 95 to 105 kmh then the car shakes bad. The passenger seat literally vibrates. We ruled out warped brake rotors by expanding the calipers and testing it, and I think we ruled out transmission by driving up to 120kmh then putting it in nutral and letting it coast into that speed range...it still shakes bad...bellow 95 and above 105 is perfect. I have spent $300 on testing this thing so far..please help me...