Restore Your Speedometer to Correct, Accurate Operation. These Gears Fit In The Transmission and Drive the Speedometer Cable. We recommend checking your current gear for color and number of teeth. If your speedometer reads faster than actual speed, then choose a gear with one more tooth per 5 MPH error. If it reads slow, then choose a gear with one less tooth per 5 MPH error. Generally used with 3.36 gear ratio and manual transmission. Can also be used with automatic transmissions.