There are three common types of U-joint designs.

1. Single U-joints retained by either an inside or outside snap ring.

2. Coupled U-joints commonly called the double-Cardan constant velocity joints.

3. U-joints held in the yoke by U-bolts or lock plates.

Single Universal Joint

The single Cardan/Spicer universal joint is also known as the cross or four-point joint. These two names aptly describe the single Cardan, since the joint itself forms a cross, with four machined trunnions or points equally spaced around the center of the axis. Needle bearings used to abate friction and provide smoother operation are set in bearing cups. The trunnions of the cross fit into the cup assemblies and the cup assemblies fit snugly into the driving and driven universal joint yokes. Universal joint movement takes place between the trunnions, needle bearings, and bearing cups. No movement should take place between the bearing cup and the hole in the universal joint yoke. The fit between the hole in the yoke and the bearing cups is known as a press-fit. Retaining rings hold the bearing cups in place in the universal joint yoke.

Replacing a single U-joint requires that the technician know more than the make and model of the vehicle. It might be necessary to know the type of U-joint and the yoke span to obtain the proper replacement part.

Spicer Style In this angle U-joint design an outside snap ring fits into a groove machined in the outer end of the yoke. The bearing cups for this style are machined to accommodate the snap ring.

Mechanics or Detroit/Saginaw Style In this design, an inside snap ring or C-clip fits into a groove machined in the bearing cup on the side closer to the grease seal. When installed, the clip rests against the machined inside portion of the yoke. The snap ring in the Detroit/Saginaw style is injected nylon. That is, the snap rings are retained by nylon injected into the retaining ring grooves.

Cleveland Style In an attempt to combine U-joints to obtain more coverage, the Cleveland style is used for some applications. The bearing cups for this U-joint are machined to accommodate either Spicer or Mechanics style snap rings. If a replacement U-joint comes with both style clips, use the clips that pertain to your application.

Double-Cardan Universal Joint

Most often installed in front-engine rear-wheel-drive luxury automobiles, the double-Cardan universal joint smoothly transmit torque regardless of the operating angle of the driving and driven members. It is, therefore, classified as a constant velocity universal joint. Observe the left and right universal joint centerlines. The bisect the angle made by the input driving and the output driven universal joint. Constant velocity operation is the result.

To double-Cardan universal joint is made up of two Cardan universal joints linked together by a coupling yoke. A centering ball socket is inside the coupling yoke between the two universal joints. This ball and socket maintain an axial relationship between the two universal joints. The ball joint divides the universal joint operating angle into two equal parts, so each universal joint operates at half of the operating angle. Since the two universal joints operate at the same angle, vibrations and fluctuations in speed from the front joint are nullified by the vibrations and fluctuations in speed from the rear universal joint. The canceling angles produce a smooth transfer of engine torque. The double-Cardan joint is often a vital part of a two-piece drive axle shaft.