Universal Joints

A universal joint, or U-joint, connects sections of the propeller shaft and lets the shaft transmit torque while changing angle. As a commercial vehicle moves over uneven ground and its suspension flexes, the U-joints allow the driveline to bend while still carrying power to the axle.

A U-joint is a cross-shaped part with bearing caps on each end that let it pivot. Mounted between shaft sections, it transmits the engine torque from one section to the next even when the two are at an angle to each other. This lets the propeller shaft follow the movement of the axle without binding.

The needle bearings inside the caps wear from friction and loss of lubrication, producing play in the joint. Signs include vibration, a clunk when accelerating or shifting, and a squeak that changes with speed. A worn U-joint can eventually seize or break and interrupt power, so it should be inspected and replaced early. Keeping it greased, where it has a grease fitting, extends its life.

The correct joint depends on the propeller shaft and its series size and dimensions. Confirm the part against the vehicle specification before fitting.