There are many types of U-Joints, some of which are extremely complex. The simplest category referred to as Cardan U-Joints, are either block-and-pin or bearing-and-cross types.
U-joints are available with two hub styles solid and bored. Sturdy hubs don’t have a machined hole. Bored hubs include a hole and are known as for the hole shape; round, hex, or square style. Two bored variations that deviate from these common shapes are splined, which have longitudinal grooves inside bore; and keyed, which have keyways to avoid rotation of the U-joint on the matching shaft.
Using the incorrect lube can lead to burned trunnions.
Unless usually recommended, use a high quality E.P. (intense pressure) grease to support most vehicular, commercial and auxiliary travel shaft applications.
Mechanically flexible U-Joints accommodate end movement by using a telescoping shaft (square shafting or splines). U-Joints function by a sliding movement between two flanges that happen to be fork-designed (a yoke) and having a hole (vision) radially through the eye that is linked by a cross. They allow larger angles than versatile couplings and are being used in applications where substantial misalignment needs to be accommodated (1 to 30 degrees).
Always make sure new, fresh grease is evident in all U-joint seals.
Can be caused by operating angles which are too big.
Can be caused by a bent or perhaps sprung yoke.
Overloading a drive shaft could cause yoke ears to bend. Bearings will not roll in the bearing cap if the yoke ears are not aligned. If the bearings quit rolling, they U Joint remain stationary and can “beat themselves” in to the area of the cross.
A “frozen” slip assembly won’t allow the travel shaft to lengthen or shorten. Each and every time the travel shaft attempts to shorten, the load will be transmitted in to the bearings and they will indicate the cross trunnion. Unlike brinnell marks due to torque, brinnell marks that happen to be the effect of a frozen slip are often evident on the front and back surfaces of the cross trunnion.
Improper torque about U-bolt nuts could cause brinelling.
Most manufacturers publish the recommended torque for a U-bolt nut.
Improper lube procedures, where recommended purging isn’t accomplished, can cause a number of bearings to be starved for grease.