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 at the extension housing seal is suspected, 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 is attached; if it is leaking, transmission lubricant will be evident on the front of the driveshaft and may be dripping from the rear of the transmission. Remove the driveshaft, then using a soft-face hammer, carefully tap off the dust shield if equipped, taking care not to distort it. Using a screwdriver, pry bar, or seal removal tool, carefully pry out the extension housing seal without damaging the splines on the transmission output shaft. Install the new extension housing seal using a seal driver or a large deep socket, ensuring it is driven into the bore squarely and completely seated, then reinstall the dust shield if equipped by carefully tapping it into place. Lubricate the splines of the transmission output shaft and the outside of the driveshaft sleeve yoke with multi-purpose grease, then install the driveshaft, being careful not to damage the lip of the new seal, and lower the vehicle. The transmission speed sensor is located on the left side of the transmission extension housing for 2WD models or on the left side of the transfer case extension housing for 4WD models, and information regarding O-ring replacement for the transmission speed sensor is available.