We stock many GM, Ford, and Dodge and Chrysler speedometer gears. If changing the rear differential gear ratio, it may change your speedometer calibration. These gears are easily interchangeable to get the speedometer to read correctly. We also have speedometer clips, brackets, sensors, and housings. We also have a program that if you supply us with the rear tire size (ex. 235/60/ R15), rear differential axle ratio (ex. 3.42), and type of transmission, we can supply you with the necessary speedometer drive and driven gears to have your speedometer read correctly.