Raise the vehicle and support it securely on jackstands. Remove the driveshaft. Use a seal removing tool to take out the oil seal from the end of the extension housing, or alternatively, a wide-bladed screwdriver or chisel can be employed to carefully tap around the flange of the oil seal and separate it from the transmission extension housing. Before installing the new seal, inspect the sealing surface of the universal joint yoke for scoring; if any scoring is found, replace the yoke. Check the counterbore of the housing for burrs and remove them with emery cloth or medium grit wet-or-dry sandpaper. Coat the outside diameter of the seal with RTV sealant. Install the new seal into the extension housing using a large socket or length of pipe of the proper diameter, or a blunt punch and hammer can also be used to tap the new seal into the bore. The remainder of the installation follows the reverse of the removal procedures.