Ford parts gears with a Dobbs Ford invoice and packaging

Using the mfr's diameter in Liquid's calculator, the gray 19-tooth gear in the car should be correct, but the speedo showed ~9% high. Using the tire's rolling diameter of 25.79" (back-calculated from the RevsPerMile), it recommends the orange gear. But even after installing the orange gear, it's still ~4% high at highway speeds. Below 55, it's dead-on.



The drive gear in the transmission tailhousing has 8 teeth.

Owner caption November 2010 · Photo 898 of 980