I have a completely stock 2001 F150 (wheels, rear end, etc.). I recently test drove the truck with my code reader displaying the vehicle speed along side my GPS and they matched exactly at all speeds.

However, the speedometer is about 4 MPH high compared to the GPS/computer. It's not a big deal since the computer knows the correct speed but is annoying. Is there a way to calibrate just the gauge when the computer is accurate?

Thanks.