(Updated on April 22, 2020)
The constant-velocity joints, also known as the CV joints, assist in the process of allowing power from the transmission and driveshaft to be transferred over to the wheels of a vehicle. More specifically, the constant-velocity joints allow this to happen through the variable angles which exist between the driveshaft and the wheels. That way, the rotational speed of the wheels will not be affected by the rotating angled joints because there is no more friction than there would be if they were straight joints.
Constant-velocity joints can be found within the wheels of the vehicle that turn. So, if you are driving a front-wheel drive vehicle, then it is likely going to have constant-velocity joints in those two front wheels. If you are driving a rear-wheel drive vehicle, then these joints will be in the back two tires.
5 Types of CV Joints
You might assume that all constant-velocity joints are the same. The truth is there are 5 main types of constant-velocity joints which can be used in vehicles. There are actually more than 5 altogether, but the joints listed below are the most commonly found ones. Each type of joint works well for specific types of vehicles.
Tripod Joints and Ball-Type Joints – Plunge joints can be either a tripod joint or ball-type joint. The former features a spider (also known as a tripod) that has three trunnions. These are components with spherical rollers attached to needle bearings. You would usually use tripods as inner plunge joints for vehicles that have front-wheel drive. As for the ball-type joints, they have a double-offset style and cross groove style.
Rzeppa Joints– This is an outer constant-velocity joint which is frequently used in vehicles. There are 6 spherical balls on this joint which reduce the operating angle by 50%. The teeth of the gears do not transmit the torque across the joint. What happens is the balls will go against their tracks. This was one of the first constant-velocity joints ever invented. In 1920, an engineer named Alfred H. Rzeppa developed this joint and it has been used ever since.
Inboard / Outboard Joints – Front-wheel drive vehicles have drivetrains with two constant-velocity joints per half shaft. There is an inner constant-velocity joint and an outer constant-velocity joint. The inner constant-velocity joint is near the transaxle. The outer constant-velocity joint is near the wheel. If you are driving a rear-wheel drive vehicle, the inboard joint is near the differential and the outboard joint is closer to the wheel.
Fixed / Plunge Joints– Front-wheel drive vehicles have an inboard joint called a plunge joint and an outboard joint called a fixed joint. Usually, the fixed joint will do most of the work because it helps maneuver around angles as you’re steering the wheel. Rear-wheel drive vehicles will use the plunge joints more. If there is an independent rear-wheel suspension, each axle shaft will have one plunge joint.
Fixed Tripod Joints – You might come across certain front-wheel drive vehicles with outer joints that are fixed tripod joints. The trunnion will be mounted onto the outer housing of the joint. There is an open tulip in the input shaft that has three different roller bearings that are turning against it. A steel spider is responsible for keeping the joint together by locking it in place.