Speedometer Gear Calculator

When changing the wheels and/or tires on a vehicle, it can occur that your speedometer is now reading inaccurately with the GPS.
This can happen because not all tires are manufactured at exactly the same height.
Or because the tires/wheels you placed on your vehicle were not the factory standard.
If the vehicle has a mechanical speedometer, replacing the speedometer driven gear (in the speedometer gear housing in the tail or transfer case) could be necessary to recalibrate it.

The number of teeth needed for the new driven gear will vary depending on the size of the rear tires, the vehicle’s rear axle ratio (rear end ratio), and the drive gear tooth count (on, or machined onto, the transmission output shaft).