U Joint

There are many types of U-Joints, some of which are incredibly complex. The easiest category referred to as Cardan U-Joints, are either block-and-pin or bearing-and-cross types.

U-joints are available with two hub designs solid and bored. Sound hubs do not have a machined hole. Bored hubs include a hole and are named for the hole condition; round, hex, or sq . style. Two bored models that deviate from these common shapes are splined, that have longitudinal grooves in the bore; and keyed, which have keyways to avoid rotation of the U Joint U-joint on the matching shaft.

Using the wrong lube can result in burned trunnions.
Unless otherwise recommended, use a high quality E.P. (serious pressure) grease to program most vehicular, professional and auxiliary travel shaft applications.
Mechanically flexible U-Joints accommodate end movement by simply by using a telescoping shaft (square shafting or splines). U-Joints function by a sliding motion between two flanges that are fork-shaped (a yoke) and having a hole (attention) radially through the attention that is linked by a cross. They enable larger angles than adaptable couplings and are used in applications where substantial misalignment should be accommodated (1 to 30 degrees).

Always make sure fresh, fresh grease is evident in all four U-joint seals.

Can be due to operating angles which are too big.
Can be the effect of a bent or sprung yoke.
Overloading a drive shaft can cause yoke ears to bend. Bearings will not roll in the bearing cap if the yoke ears aren’t aligned. If the bearings prevent rolling, they remain stationary and can “beat themselves” in to the surface of the cross.
A “frozen” slip assembly will not allow the travel shaft to lengthen or shorten. Each time the travel shaft tries to shorten, the strain will be transmitted into the bearings and they will indicate the cross trunnion. Unlike brinnell marks caused by torque, brinnell marks that happen to be the effect of a frozen slide are always evident on leading and back floors of the cross trunnion.
Improper torque about U-bolt nuts can cause brinelling.
Most manufacturers publish the recommended torque for a U-bolt nut.
Improper lube procedures, where recommended purging is not accomplished, can cause a number of bearings to be starved for grease.