U-joints are important to your truck. Without them, the drive shaft could not spin and move up and down with the suspension at the same time. Replacing a U-joint is important if you notice clucking noises coming from the rear when shifting into gear or stepping on the gas or if you notice a vibration coming from the rear end. If the U-joint is not spinning true, it will eventually fail. The joint will wear and bind until it finally breaks and the potential for it to damage the drive shaft, differential or transmission is high.
Raise the rear of the vehicle with a jack and support it on a set of jack stands. Be sure to use jack stands that are rated high enough for an Expedition, which are big and heavy vehicles.
Place the transmission in neutral. Mark the position of the drive shaft and yokes with a paint marker so they can be reassembled in the same position. The shafts are balanced, and if the orientation is changed, vibrations could result.
Remove the four retaining bolts at the differential end of the drive shaft with a wrench. You may need to turn the drive shaft to access all four bolts. Drop the drive shaft down and slide it out of the rear of the transmission.
Locate the retaining clips on the U-joint caps and remove them with a pair of pliers. Squeezing the tabs on the spring clip together will allow it to be removed from the drive shaft yoke.
Remove the U-joint from both ends of the drive shaft using a U-joint press. If you do not have a U-joint press, you can rent one at many auto parts stores. There are several styles of U-joint presses available, so be sure to read the directions that come with the press to correctly use it.
Install new U-joints in both ends of the drive shaft and press the caps into place with the U-joint press. Replace the retaining clips with the new ones that came with your U-joints and be sure that they snap into the groove in the yoke.
Align the mark you made on the transmission with the mark on the drive shaft. Insert the slip yoke into the transmission, being careful not to damage the splines on the shaft as you slide it into the case.
Raise the rear of the drive shaft and align the mark you made on it with the mark you made on the rear differential. Install the four mounting bolts and tighten them evenly with a crisscross pattern. Torque the bolts to 83 foot-pounds with a torque wrench.
Raise the rear of the truck off the jack stands using your jack. Remove the jack stands and lower the truck to the ground. Test drive the truck to verify that there are no vibrations in the rear end.
