i just bought a car, and the guy i bought it from said the speedometer says the car is going 10-15 mph faster than it actually is, and he also said it just happened, no gears in the car, same size wheels, but the transmission was worked on, but he said it did not happen right at this time. What could it be? and how do i get it fixed? thanks for the help

 

What kind of car/transmission.
Could be your spedo cable.

That seems like a pretty big jump in speed difference. Trying seeing if your dealer would reflash your computer. Or do it yourself with the right cable and software. (ie. ALDL cable and C.A.T.S tuner.)

 

Without basic info about the car - year, model, engine, tranny and any major mods, its almost impossible to answer some of these questions. Why not add a "signature" with that info?