TCI speedometer gear housings are designed to replace the OEM gear housing in your automatic transmission. They install easily into the removable section of the rear tail housing of the transmission. The TCI speedometer gear housings are available in different tooth combinations and are identified by their color. Upgrading to larger diameter tires? changing ring and pinion gear ratios? make sure you use one of these TCI speedometer gear housings to keep track of your speed accurately.