I think there is a little plastic gear that you can replace where the speedo cable goes into the transmission or transfer case(not sure which). If you talk to a service shop they should be able to set you up. Superlift also makes a Speed sensor calibrator if your speedometer is electronically controlled. It is a four-wire hook-up that goes in-line with speed-sensor and transfer case or transmission. You can check it out at www.superlift.com or give them a call at 800/551-4955.