Like most vehicles, a Jeep's driveshaft is connected to the differential through a universal joint, also known as the U-joint. Over time, the grease within the joint will run out and cause the joint to wear down, requiring you to replace it. Changing a U-joint on any vehicle is not an easy task, and the Jeep is no exception. You will need a professional-level garage or workspace. Check with your mechanic in case there are any slight differences in the replacement process for your specific model.
Raise the Jeep on its rear end and support it on jack stands. Block the front wheels with wheel chocks and make sure the parking brake is off with the transmission in Neutral.
Mark the driveshaft's relationship to the differential with paint where the two yokes are connected.
Remove the bolts and straps for the universal joint with a flare-nut wrench. Insert a screwdriver into the joint as you remove the bolts to keep the driveshaft from turning.
Lower the driveshaft's rear end and slide the front end out of the transfer case or transmission to remove it from the vehicle.
Wrap a plastic bag around the transfer case or transmission to prevent loss of fluid.
Pry the snap rings out of the U-joint spider using needle-nose pliers.
Place the driveshaft within a bench vise Insert a wrench socket with the same diameter as the U-joint bearing caps into one of the caps and place a smaller socket inside the other cap.
Press the vise against the U-joint and the two sockets to force the first bearing cap out; stop the vise before the cap comes all the way out of the yoke and use large pliers to remove it the rest of the way.
Switch the position of the two sockets and repeat the above step to remove the other bearing cap.
Pack the new bearings for the joint with grease, following the specific lubrication instructions included with the universal joint service kit.
Place the new spider/cross in position within the yoke and partially install one of the bearing caps. Fit the spider on the bearing cap and then partially insert the other cap.
Align the spider within the yoke and press the bearing caps into position.
Install the snap rings into position with the needle-nose pliers. If they don't fit, hit the yoke sharply with a hammer to release tension within the yoke.
Connect the grease fitting to the spider, making sure it faces toward the driveshaft. Fill the universal joint with grease, making sure you don't overfill it.
Remove the bag from the transmission/transfer case and then slide the driveshaft's front end in position on the transmission/transfer case. Raise the shaft's rear end into position with the differential, making sure the marks you made are lined up.
Connect the driveshaft to the differential using new bolts and straps with the flare nut wrench.
Lower the truck off the jack stands using the floor jack.
