Phoenix Transmission Products 700R4 - TH-2004R - TH-350 - 4L80E... Popular Automotive Math Formulas and Conversions RPM = mph X gear ratio X 336 divided by tire diameter. To..., all the shifts are performed hydraulically. We wire our transmissions up internally so all you need to do is attach a 12 volt source to the supplied pigtail and the trans will do... in the most efficient way possible. What is COMPUSHIFT? COMPUSHIFT is a revolutionary, state of the art product designed by HGM Automotive Electronics Inc. The COMPUSHIFT Transmission...