The 3 Most Common Causes of U-Joint Failure
While any rear wheel drive vehicle can have a universal joint (u-joint), they’re typically found on pickups and SUVs. U-joints connect the driveshaft to the transmission and rear differential, and they allow for a change in the angle of the driveline. This way, the vehicle’s rear axle can move up and down without breaking the driveshaft.
When a u-joint begins to fail, it’s normal to notice clunking during gear shifts, grinding during a turn, or even vibrations at higher speeds. When a vehicle requires a replacement u-joint, it’s often helpful if a service advisor or technician can explain the various possible causes of failure.
Here are the three most common causes of u-joint failures:
1. Normal Wear and Tear
Just about everything on a working automobile will fail over time, and the u-joints are no exception. U-joints experience quite a bit of wear and tear, especially on vehicles that go off-road or that tow frequently.
Proper lubrication can greatly extend the lifespan of your vehicle’s u-joints, and u-joints that can be lubricated will have recommended maintenance intervals. However, some u-joints are “closed” or sealed designs that do not allow added lube.
Misalignment of the driveshaft can happen when modifications are made to the rear differential or the transmission’s mounting. Misalignment will create excess vibration that can literally “shake” the u-joint apart, damage seals that reduce lubrication, and ultimately cause the u-joint to fail.
Adding a lift kit or a set of oversized tires can shorten the lifespan of a u-joint. If a vehicle is altered in this way, it’s a good idea to inspect the u-joints and make sure the angles are still within spec.
3. Loose Connections
Sometimes, the bolts holding the u-joints in place – either to the driveshaft or to the transmission or differential – can come loose or fall out completely. This usually happens because of corrosion, excessive jolting or vibration, or because the bolts were not properly torqued into place. A worn or cracking transmission or differential housing can also cause this.
Of course, u-joint failure isn’t limited to these three causes. Over-torquing can cause damage, as can extreme duty (racing, towing more than the recommended payload, aggressive off-roading, etc.). Vehicles with heavily modified engines can also cause u-joint failures.
Knowing the Cause of Failure Is Key To Correct Replacement
When it’s time to replace a u-joint, it’s essential to know the cause of the existing u-joints failure. If, for example, a vehicle’s engine or suspension has been modified, replacing the OE u-joint with another OE-spec unit is not going to fix the problem.
Likewise, if the vehicle owner isn’t aware of the importance of u-joint lubrication, they may end up needing another set of u-joints much sooner than expected.