How to replace your classic’s universal joints

These instructions are for cars with open drivelines. For cars equipped with closed, torque tube drivelines, consult a shop manual to determine how to remove and replace the U-joints. Even on cars with open drivelines, there are variations on the cross-and-yoke design, and there were also the ball-and-trunnion types used as front joints on prop shafts in ’40s-era Chrysler products.

Out with the old

Put your car up on sturdy jack stands and make sure it is stable before climbing under it. Never work on a car with only a jack supporting it. You invite disaster if you do. Now roll to the rear and, and using a file or china marker, mark the prop shaft in relation to the rear yoke of the universal joint so you can put the prop shaft back in oriented the same way it came out.

Next, roll up to the front and mark the front U-joint as well. It is possible to swap the prop shaft end for end on some cars, with unfortunate consequences, but more importantly you don’t want the prop shaft rotated 180 degrees out from where it was originally when you reinstall it, because the driveline is balanced as it is.

Split the rear universal joint, leaving the rear yoke attached to the differential. Pull the prop shaft back away from the rear of the transmission. There is a splined, tubular slip joint on the front of the prop shaft to allow it to change lengths as required when the axle bounces up and down. At this point, the next step depends on what type of U-joints your car is equipped with. Some types of joints can merely be unbolted and replaced.

On these types of U-joints, you simply bend the little sheet metal locking tabs away, and then unbolt the U-bolts or bearing caps. Tape the old U-joint together as you remove it, so you won’t spill the tiny needle bearings out of it and end up skating around on them in your shop for the next month. Put a little grease in each of the new U-joint’s bearing caps, then bolt them back in place and tighten them evenly. Use new locking devices, and bend the tabs up to secure the bolts.

Install the prop shaft so it is aligned according to your reference marks, and you’re all done.

If your car uses the conventional, cross and yoke type U-joint that is pressed in (and most rear drive cars made in the last 40 years do use this type), to extricate them from the prop shaft you will first need to remove the bearing cap lock rings using a pair of snap ring pliers. Your replacement U-joint kits will contain new locking rings, so don’t attempt to reuse the old ones.

Getting it apart

Before you lift the cross out of the bearing caps, note which way the zerk grease fitting faces so you can put the new universal joint in the same way. If oriented the wrong direction, the zerk fitting could interfere with the U-joint’s range of motion. Next, press the bearing caps out of the yoke by placing one cross of the yoke horizontally across the open jaws of the vice, and then tapping on the vertical cross yoke with a soft brass hammer to drive the yoke down, thus forcing the bearing cap out of the yoke.

Once the bearing cap protrudes sufficiently, flip the prop shaft over and tap the yoke the other way until the bottom cap protrudes. Then just grip each bearing cap in turn with the vice, and worry it out by moving the prop shaft yoke back and forth and pulling up on it.

Once you have the prop shaft and slip joint yoke apart, place the ends of the steel cross on the vice jaws and tap the yoke to drive out its bearing caps. When they protrude sufficiently, grip them with the vice and pull them out. Be careful while you are working that you don’t disturb any balance weights attached to the prop shaft. Inspect the yokes for burrs or ridges that might cause problems when pressing in the new bearing caps. It is a good idea to dress the edges of the holes in the yokes with a fine file. Smear a very light coat of grease inside the bearing cap holes in the yokes.

In with the new

If your new U-joint has a zerk fitting installed on it to allow it to be lubricated (some replacement joints do not have a fitting), remove the fitting temporarily so pressure will not build up during installation. If the new U-joint is not freshly greased inside, smear a light coat of grease in each bearing cap, but don’t overdo it. If you put in too much grease, hydraulic lock may occur when you try to press in the new bearing caps.

Press in the bearing caps using your vice, being careful not to let the needle bearings slip around inside. Use a socket as a drift small enough to fit into the holes for the bearing caps, but large enough to spread the load evenly in order to press the bearing caps in far enough to allow you to install the retaining clips.

Chances are that once installed, your new universal joints will move a bit stiffly. To set them properly, take a hammer and drift and firmly tap once at each intersection of each cross. Test your U-joints one more time to make sure they are free and feel right. Finally, coat the splined slip joint inside, and then outside, with wheel bearing grease before reinstalling the prop shaft.
Take your car out for a test drive. It should be smooth and silent with no vibration. If there is a minor imbalance in the prop shaft causing a slight vibration, a large worm-drive hose clamp can be installed around the prop shaft, and the screw mechanism repositioned until the vibration is minimised.

Click through to the next page for an illustrated guide

Guide to replacing universal joints

File or mark a line in the prop shaft and slip joint yoke so you can reinstall them properly aligned with one another
Use special pliers made for the task, or needle nose pliers, to remove locking clips on bearing caps
Remove grease fitting from the steel cross
Place the prop shaft yoke on vice and tap slip-joint yoke with a brass hammer to remove the bearing caps
Grip each bearing cap with your vice, and work the cap free by moving the yoke back and forth while pulling up
Bearing caps will just pop loose with a little effort
Lift out the steel cross and work the final bearing cap loose using the vice
Take your new universal joints apart and make sure the bearings are properly greased
This is about how much fresh grease should be in each cap
It is not necessary, but I like to give the prop shaft a coat of Rustoleum rust resistant paint to protect it
Make sure grease fitting opening is facing correctly, then insert a bearing cap and yoke
Insert the cross to keep the needle bearings straight. Gently press in each bearing cap until flush using the vice
Use a socket as a drift to push the bearing caps in far enough to install the locking clips
Use a hammer and drift to wrap the cross once at each intersection to set the joint properly
Tape the rear U-joint together to keep bearing caps from falling off before connecting the U-joint at the differential
Use wheel bearing grease to lubricate splines in the slip joints
Grease the outside of the slip joint as well, so it won’t damage the transmission rear bearing seal when you install it
Disconnect the rear universal joint at the differential by removing U-bolts
The front end of the prop shaft just slips out of the rear of the transmission

Words & Photos: Jim Richardson