Universal Joint Kits

Functions of Universal Joints

Universal joints provide the connection between the gearbox output shaft and the driveshaft. They are placed at both ends of the driveshaft depending on the power transmission system of the vehicle. Thus, the joint provides support to counter the height difference (with respect to the ground) between the output shaft and the rear axle which occurs due to the road conditions, and it is an important part to help the transmission of rotational power between the shafts in different axes. Universal joints are classified into different types according to their areas of use or their structure. The most common among them are cross-type joints. They consist of needle rollers. These are positioned inside the bearing cap of the joint which connects the joint with the driveshaft yokes. The rollers engage tightly around the trunnions of the joint. Then, they are held by a snap ring for each trunnion at their engagement point. Thanks to this layout, the joint and the driveshaft yokes are put in a position so that they can perform a compound movement.

Lubrication of Universal Joints

One of the most important factors for a joint is lubrication. They have to be lubricated regularly in order to use them for a long period of time. Using a grease pump, joints can be lubricated through their grease fitting. The grease supplied from this fitting reaches the holes in the trunnion and allows the lubrication of the bearings. Thus, the most sound and ideal joint movements are achieved. It is possible to purge the seals of the joint and they should be purged while lubricating. For extensive periods of use, high quality joints should be preferred. Therefore, you should prefer working with successful and reliable companies in their field when you are purchasing universal joint kits. This would help the vehicle to move as a whole and as rigid as possible.

Universal Joint Types According to the Area of Use

Variable Velocity Joints:
These are classified into two groups as cross-type and ball-trunnion type. The most commonly used type of joint is the cross-type. Ball- trunnion type joints have spherical or ball-shaped bearings instead of the cross bearings. ball-trunnion joints allow a flexible operation of the shaft and also allow the shaft to move forward and backward.

Constant Velocity Joints:
In rear-wheel drive vehicles, the angles that provide assistance in the transmission of the power received from the gearbox output shaft are quite small, as a result of that, the transmission with a variable velocity joint does not pose major problems. However, in front-wheel drive vehicles, the angles generated as a result of changing the direction of the vehicle (especially angles which exceed 30 degrees) may cause changes and fluctuations in the vehicle velocity. For that reason, constant velocity joints are used for a smoother and more versatile operation. This instability introduces difficulties in steering, causes skidding, wear and tear on the corners of the tires. Thus, constant velocity joints are being developed to be used in front-wheel drive vehicles. These joints are classified into three groups: Rzeppa constant velocity joint, Bendix - Weiss universal joint and Tracta constant velocity joint.

Universal Joint Types According to their Structure

Cross-type joints can transfer torques and have a deviation angle up to 15°.

Ball joints have lower costs, are maintenance-free and are used as shock absorbing elements. Their deviation angle is 5°.

Tripod joints are joints that can slide synchronously and they are used in driveshafts and axle shafts. They have deviation angles up to 22°, and they can allow axial sliding up to 30mm.

What is a Slip Joint?

These are internally splined joints which allow the increase and decrease of the shaft length. In the rear-wheel drive vehicles, the rear axle moves up and down depending on the road condition. As a result of that, the distance between the gearbox and the differential changes continuously. Therefore, the length of the shaft has to extend or shorten accordingly. Slip joints connected to the shaft allows these changes in distance between the gearbox and the rear axle.

Joint Failures

If the slip joint is too dry and not lubricated, during the transmission of the initial movement to the rear, such as in the case of starting and moving the vehicle from a stationary position, an impact sound can be heard. If that is the case, lubricate the joint. Using a multi-purpose grease would be sufficient.

The seals of the universal joint may leak oil. In case of oil leaks in joints without grease fittings, you should replace it.

A clicking sound coming from underneath the engine, particularly going through speed bumps, indicate that the joint is either too tight or is bent. To determine this failure exactly, you should inspect the movement of the joint on the shaft. The joint has to be able to rotate in all directions without jamming.