Oil leaks frequently occur due to wear of the extension housing oil seal or the transmission speed sensor seal, and replacement of these seals is relatively easy, as repairs can usually be performed without removing the transmission from the vehicle. If a leak is suspected at the extension housing seal, raise the vehicle and support it securely on jackstands. The extension housing seal is located at the rear end of the transmission, where the driveshaft flange is attached; if leaking, transmission lubricant will drip from the rear. Remove the driveshaft, support the transmission with a jack, remove the crossmember mounting bolts, and lower the transmission slightly to gain access to the transmission flange. Use a special tool to lock the output flange in place and remove the bolt, then use a puller to remove the flange along with the plastic retainer and O-ring. Carefully pry out the extension housing seal using a screwdriver, pry bar, or seal removal tool, ensuring not to damage the splines on the transmission output shaft. Install the new extension housing seal with a seal driver or a large deep socket, driving it into the bore squarely and ensuring it is completely seated. Reinstall the flange and nut or bolt, tightening until the flange is seated; for 5-speed models, remove the nut, install a new O-ring and plastic retainer, then reinstall and tighten the nut or bolt to the specified torque. Finally, install the crossmember and then the driveshaft. The transmission speed sensor is located on the transmission extension housing, and information regarding O-ring replacement for the transmission speed sensor is available.