Okay guys here is a calculator that I made on Excel. It allows you to enter in gear ratios for each transmission speed, transfer case speed, differential ratio, and then tire size. Then it tells you engine RPM and speed in MPH for each. The default setting are for an R-151f transmission with dual transfer cases with 4.7 gears in one, but everything is editable. Hope this helps. Thank Big mike for helping me get this uploaded.