I have changed my VR Senators diff ratio to 3.73, does this affect the trip computer at all, how can I alter the trip computer to suit the new ratio?
Calibrate The trip computer allows a + or - 25% calibration adjustment to both the distance and fuel flow calibration numbers. If the default number was accurate before, then that should give sufficient adjustment to compensate for the change in overall gearing. Follow the distance calibration process, and all should be right. This calibration won't compensate the speedo though.
You will have to change the gear in your transmission that connects to the speedo cable to suit your change in gear ratio, and then your speedo will be correct, as will your trip computer..