mb7

I have a 2008 GT, and my speedometer is off by quite a bit.. It showed on the ford certified pre-owned sheet to have the 3.55 gear ratio from the factory. If my speedometer is reading 90mph, my gps actual is around 82mph. The only thing that I could think of that would throw the computer off that bad, was if someone changed the gear ratio on the car without calibrating the computer.

My question is this.. If I'm running 70mph actual on the highway with a 3.55 ratio, what should my round about rpms be? And what would they be if someone had changed the axel ratio to 3.73?

Also, I have a handheld diablo programmer, what could I do to calibrate my speedometer? This is racking up more miles on my car than I am actually driving.

mb7

Forgot to mention, my car is a 5-speed manual.

eddypython

ur predator can fix this. try adjusting for the 3.73 and see if that fixes it. If it was 4.10's u'd know

mb7

Nobody on here has 3.73s?!