In order to calculate the engine RPM based on ring gear and pinion gear ratio, speed and tire height, this calculator makes the following assumptions:
- You may not be sure of the type of transmission you are currently using. The results will then be:
- Automatic transmission in Drive
- Automatic transmission in Overdrive
- 3-speed manual transmission in 3rd gear
- 5-speed (or higher) manual transmission in the last gear
- The ratios used for the transmissions are 0.70 for the automatic and 0.80 for the manual
- You know the ring gear and pinion gear ratio. See the Gear Ratio calculator in the Spicer Tool Kit to determine your ratio.
- You know the tire height in inches. See the Tire Height calculator in the Spicer Tool Kit to determine your tire height.
- The speed will be the vehicle speed, measured in miles per hour (MPH).