Oil leaks can occur due to wear of the extension housing oil seal and bushing, as well as the speedometer drive gear oil seal and O-ring. These seals can be easily replaced without removing the transmission from the vehicle. The extension housing oil seal is located at the rear of the transmission where the driveshaft is attached. If leakage is suspected, the vehicle should be raised and supported securely on jackstands. The oil seal can be pried out of the transmission using a screwdriver or pry bar, or a special removal tool may be required. The new oil seal should be installed using a large socket or pipe as a drift. The splines of the transmission output shaft and the outside of the driveshaft sleeve yoke should be lubricated with lightweight grease before installing the driveshaft. The speedometer driven gear housing or vehicle speed sensor is located on the side of the extension housing. To remove it, the speedometer cable or electrical connector should be disconnected, and the hold-down bolt should be removed. The seal and O-ring can be checked for leaks by looking for transmission oil around the cable housing. The vacuum modulator O-ring can be replaced by removing the vacuum line, hold-down bolt, and modulator. The old O-ring should be removed and the new one should be coated with clean ATF before installation. The manual lever also has a seal, but it is recommended to take the vehicle to a qualified repair shop for replacement. To replace the manual lever seal, the shift linkage should be disconnected and the old seal should be pried out using a small hooked tool. The new seal should be driven into place using a deep socket and hammer. The shift linkage should be reconnected and adjusted before refilling the transmission. Finally, the vehicle can be lowered by removing the jackstands.
