The speedometer in my '96 gt is way off. It shows im going 150 when im only going 35-40. Anyone know what might possibly be wrong?

 

what does your speedo say when your parked? when you get moving does it immiedately jump to 150? or does is it at like 100 while your parked then immiedately shoot to 150?

cuz someone could have possibly removed the needle to take off/put on a new guage face before they sold the car and didnt put the needles on correctly.