SO I have given up on this thing. Today I set the tire size to 32" and the speedometer registered slow. So I then set the tire size to 31.5" - tire sizes are in 1/2" increments only on this screen. The speedo registered too fast. So I think OK, all I have to do is figure out a proper tire size that ...

I finally received my back ordered u7180 for my '01 Duramax. The firmware is at v9r10. The truck has been lifted from stock and has a 3.73 rear end and the new tires are 315/75R16. Mathematically, the numbers verify with what the speedometer says stock compared to GPS (and cops radar).

Imagine my ...