Here are some tips and tricks about U-joint maintenance and repair:
1. There are two types of U-joints: greaseable and non-greaseable.
Equipment manufacturers specify U-joint lubrication intervals in owner’s manuals based on operating rpm, operating angle of the U-joint and in-house testing. Non-greaseable U-joints have lifetime lubrication and do not require disassembly and relubrication.
2. Some U-joint manufacturers recommend greasing U-joints until clean grease pushes from beneath each cap to purge dirty grease.
Others warn that excess purging can damage the seals and shorten U-joint life. A compromise seems is to grease until it appears from the cap seals.
3. Non-greaseable U-joints are often used in high-torque applications or where they are difficult to access.
Some folks think replacing a troublesome non-greaseable U-joint with a greaseable U-joint will improve longevity. Premature failure of non-greaseable U-joints is usually from problems with driveshaft alignment or some other mechanical problem rather than inadequate lubrication.
4. A U-joint can be rebuilt with a vise, a hammer and several appropriate-size sockets.
An easier approach is to use a commercial U-joint repair tool, like Tiger Tools’ U-Joint Puller. The pullers come in automotive, medium-duty and commercial truck sizes.
5. Over-tightening the U-bolts that hold U-joint caps can crush the cap and needle bearings inside.
Automotive and pickup U-joint bolts should be torqued to around 14 lb./ft. If using lock washers, tighten until the lock washer flattens, and then a quarter turn more. Lock nuts are tricky. When the locking part of the nut engages, it distorts torque readings and makes it difficult to accurately read torque.
6. Some U-joints use black plastic thrust washers inside their caps at the base of the needle bearings.
If the washers are missing at disassembly and the grease in the cap is sticky black goo, the caps and needle bearings have run hot and melted the thrust washers. That’s when it’s time for a new U-joint.
7. Some replacement U-joints come with an array of snap rings color-coded according to thickness.
Use color-matched pairs of the thickest snap rings possible on each side of the U-joint’s “cross” to slightly preload tension against that cap and remove all free play.
8. A properly repaired U-joint, when its driveshaft is held horizontally, should stay in line with the shaft but articulate down with slight force from a finger.
A new or rebuilt U-joint that drops under its own weight is too loose, and the excessive clearances will reduce its lifespan.
Want more shop fix-it tips and tricks from Dan Anderson?
Plastic Pop Rivets Have Taken Over the World
Not All O-Rings Are Created Equal
Tools to Keep Your Frustration Level Low with Stubborn Filters
