U Joint

There are many types of U-Joints, a few of which are extremely complex. The simplest category referred to as Cardan U-Joints, will be either block-and-pin or bearing-and-cross types.

U-joints are available with two hub designs solid and bored. Sound hubs don’t have a machined hole. Bored hubs include a hole and are named for the hole shape; round, hex, or square style. Two bored styles that deviate from these prevalent shapes are splined, that 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 superior quality E.P. (severe pressure) grease to service most vehicular, commercial and auxiliary drive shaft applications.
Mechanically flexible U-Joints U Joint china accommodate end movement by by using a telescoping shaft (square shafting or splines). U-Joints function by a sliding movement between two flanges that are fork-designed (a yoke) and having a hole (eyesight) radially through the eye that is connected by a cross. They let larger angles than adaptable couplings and are being used in applications where huge misalignment must be accommodated (1 to 30 degrees).

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

Can be caused by operating angles which are too large.
Can be caused by a bent or sprung yoke.
Overloading a travel shaft can cause yoke ears to bend. Bearings won’t roll in the bearing cap if the yoke ears aren’t aligned. If the bearings prevent rolling, they continue to be stationary and can “beat themselves” into the surface area of the cross.
A “frozen” slip assembly won’t allow the travel shaft to lengthen or shorten. Every time the travel shaft attempts to shorten, the strain will be transmitted into the bearings and they’ll indicate the cross trunnion. Unlike brinnell marks due to torque, brinnell marks that will be caused by a frozen slip are constantly evident on the front and back areas of the cross trunnion.
Improper torque on U-bolt nuts can cause brinelling.
Most producers publish the recommended torque for a U-bolt nut.
Improper lube procedures, where recommended purging isn’t accomplished, can cause one or more bearings to be starved for grease.