Not sure if you ever figured this out, but I just bought a T-Boss 760 and had the same issue. On the console above the steering wheel, you have a button A (left side) and button B (right side). Button A toggles through the odometer, hours, and trip miles. Per the manual, button B is supposed to change the display from KM to MPH but nothing happens when I press it. Then I found a Facebook post with the correct instructions. Using button A make the display show the odometer, then you just press button B and it toggles between KM and MPH. If you have the console showing anything other than the odometer, then button B does nothing. It worked for me, hope it helps someone down the road. Very annoying its not in the instructions, but also wasn't surprised.