I just put 3.73 gears in my 2000 z28. Now my speedometer is way off, the fast i go the more off it gets. I want to get it fixed but i am not sure how, i am getting all different answers. People are saying its the transmission gear i have to change and others are saying i have to get the car tuned. Does anyone know how i can solve this problem? And the cheapest way

thanks guys.