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U-Joint Repair
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     I can hear it at low speed, a scraping squeak as the old Ford coasts to a stop. As I take off again, there is a clunk from under the truck. At cruising speed something doesn't sound right, and I can feel a vibration. On my back under the truck, the U-Joints appear to be fine, but one of the front driveshaft u-joints is loose when I wiggle the driveshaft by hand. It is time to get out the tools!
 
The photos at the right are an example of a bad u-joint. The needle bearings had fallen out of the cup and the cross was using the cup as a bearing. Total failure of the cross, u-bolt, or yoke is likely if it is run for long in this condition.
 

Fortunately, replacing a u-joint is usually fairly simple. Here is how it is done.
 
   To change a universal joint, the driveshaft must be removed from the vehicle.  Soaking the u-joints and u-bolts with penetrating oil for a few days will make disassembly easier.
     Before removing the driveshaft, mark the yoke positions at both ends. When the driveshaft is reinstalled, each end should go back to its original position  so that the shaft will be phased properly. If the driveshaft is improperly phased, vibration may damage the u-joints.
     Remove the u-bolts (some vehicles use two bolts and a strap instead)  at both ends.  The bearing cups have usually rusted to the yokes and the driveshaft will not fall on you.  With all u-bolts removed, pry the axle end of the driveshaft loose from the yoke and then pull the other end free. 

NOTE:  Some driveshafts have a double cardan type CV joint at the transfer case end. Mark the position of the flanges and then remove the flange bolts. The flanges will then separate and the driveshaft can be removed. 

Manual hubs make it easy to break the front driveshaft bolts loose. Leave the case in 2WD, lock the hubs, and remove the easily reached bolts while the hubs hold the shaft steady. Then reach around, unlock one hub, rotate the driveshaft to access the remaining bolts, lock the hub, and then finish removing the bolts.

 
Next, both retainer snap ring clips must be removed. This is much easier if they have been hit with penetrating oil for several days.
   First, a screwdriver is used to loosen the snap rings by prying the ends out of the groove (right). This step is just to break some of the rust loose, it will not remove the clip. Tapping on the clip and bearing cap with a hammer and soft drift punch will also help loosen the snap ring.
    Then, use a pair of pliers to grip the ends and squeeze the snap ring enough to clear the groove (bottom left). Usually a rusted-in snap ring will slide out of the groove with a little persuasion from a screwdriver (bottom right).  If you are lucky, the clip pops out (right).  Remove the snap rings from both sides of the yoke.
      Occasionally the ends of the snap ring will break off and you must cut the snap ring into pieces with a cold chisel and dig them out of the groove with a pick.  This is every bit as much fun as it sounds! 
 

 
   To remove the cross from the yoke, select a large socket that will support the yoke flange and allow the cup to drop. In this case, a 1 3/16" socket was perfect. Then drive the cross and cups down with a hammer and a socket small enough to fit inside the yoke flange. A brass hammer is easier on the socket, but not required.
     When the cross bottoms on the yoke flange, the lower cup can be removed and discarded. Be careful not to damage the yoke by pounding the cross into it.
 
   With finesse, the cross can usually be wiggled out of the yoke.  If the yoke is too tight to allow this, turn the  driveshaft 180 degrees and knock the cap out of the other side. Be careful to keep the cross straight while removing the second cap or the yoke bore may be scored. 

 

   The yoke is cleaned and the retainer groove is scrubbed with an old toothbrush to remove rust and scale. Check for cracks in the yoke and remove any burrs from the yoke flange.
 
  When the yoke flanges are clean, it is time to reassemble the u-joint. Make sure the u-joint is oriented properly. The small caps usually go into the yoke and the large caps are u-bolted to the axle or transfer case yoke.
    Lightly grease the yoke bores to aid reassmebly. If it was possible to remove the cross with one cap still attached (as shown above) remove one of the caps that will be installed in the driveshaft yoke. With the other three caps still installed on the cross, finesse the cross into the yoke. 

NOTE: Make sure the needle bearings stay in place. Keep the needle bearings and the exposed end of the cross clean, or you will get to do this again!

 

   Inspect the new bearing cap that was removed from the cross to make sure that the needle bearings are in place. Carefully align the cap with the exposed end of the cross and press the cap into the yoke with a large vise or C-Clamp (right). NOTE: For maximum u-joint strength, you want the zerk fitting to be under compression when the driveshaft is turning to drive the vehicle forward. In the case of this driveshaft, this shaft will rotate clockwise as viewed from the end and the driveshaft yoke will be pushing against the zerk section of the cross.
    The cap will press against the cross and then use the cross to press the opposite cup into the yoke. When the cup can be pressed no farther without distorting the yoke, install the snap ring on the opposite side (below left). Then use a nut or other spacer to finish pressing the cap and complete u-joint into place (below center).  Install the remaining snap ring and test the assembled u-joint for binding (below right). 

 

Note: For u-joints that will not fit into the yoke unless both bearing caps are removed: First insert the cross without the caps, press one cap into the yoke, insert the snap ring, then turn the shaft and repeat on the other side.
 
 
 

   The completed u-joint is ready and the driveshaft can be reinstalled. BUT, for an additional $12 you can replace the u-joint at the other end while the shaft is out of the truck, so go ahead and replace it too.
     The loose needle bearings you see in this photo are from the old u-joints  -  I hope!       :-)


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Last Update: February 21, 2000