i have a 91 caprice classic with 305 engine. the other day i was driving home and noticed that the car was fine under 45mph but as soon as i gave it some gas at 45mph it would shake pretty bad. this seems to have happened out of nowhere. i always drive it in overdrive if that makes a difference. i dont know if this is a transmission issue or if it could be a sensor or what but if someone could please help i would appreciate it.