U Joint

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

U-joints can be found with two hub variations solid and bored. Stable hubs don’t have a machined hole. Bored hubs have a hole and so are named for the hole shape; round, hex, or sq . style. Two bored variations that deviate from these common shapes are splined, that have longitudinal grooves in the bore; and keyed, that have keyways to prevent rotation of the U-joint on the matching shaft.

Using the wrong lube can bring about burned trunnions.
Unless in any other case recommended, use a superior quality E.P. (excessive pressure) grease to provider most vehicular, industrial and auxiliary travel shaft applications.
Mechanically flexible U-Joints accommodate end movement simply by by using a telescoping shaft (sq . shafting or splines). U-Joints function by a sliding action between two flanges that will be fork-designed (a yoke) and having a hole (eye) radially through the attention that is linked by a cross. They let U Joint larger angles than versatile couplings and are used in applications where substantial misalignment must be accommodated (1 to 30 degrees).

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

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