Today they put my 4:10s in the car and a 23tooth speedo gear and my speedo seems to me about 10mph off at 40mph (When my dads car was going 40mph my speedo read 50mph.) I went back to the shop that did the installation and they said their was nothing i could do about it. Is their any way i can correct my speedo or do i have to just live with it. The car is a 1992 Gt vert with and AOD trans On a better note the 4:10s are great and i love the performance