Oil leaks frequently occur due to wear of the extension housing oil seal, which is relatively easy to replace without removing the transmission from the vehicle. The extension housing oil seal is located at the extreme rear of the transmission, where the driveshaft is attached. If leakage at the seal is suspected, raise the vehicle and support it securely on jackstands. A leaking seal will result in transmission lubricant building up on the front of the driveshaft and possibly dripping from the rear of the transmission. Remove the driveshaft, then use a seal removal tool or a large screwdriver to carefully pry the oil seal out of the rear of the transmission, taking care not to damage the splines on the output shaft. Install the new oil seal using a seal driver or a very large deep socket as a drift, ensuring it is driven into place squarely and completely seated. Lubricate the splines of the transmission output shaft and the outside of the driveshaft yoke with lightweight grease before reinstalling the driveshaft, being cautious not to damage the lip of the new seal.