Disconnect negative battery cable and safely raise vehicle. Place a properly sized drain pan under the extension housing, and clean the transfer extension housing seal area. To disengage the driveshaft, matchmark it to the rear axle flange, and then extract it from the device rearwards. Utilize T74P-77248-A tool or similar to remove the extension housing seal. Lubricate the inside diameter of the oil seal. Install with tool T74P-77052-A. Ensure the oil seal drain hole is pointing down when fitting it into the extension housing. Put back the leftover 'stuff' in the reverse order of removal. Ensure the marks on the driveshaft are aligned.