Constant-velocity (CV) joints are essential components of a vehicle's drivetrain system. They connect the axle shafts to the wheels and allow for smooth power transmission even at varying angles. CV joints are divided into two types: inner CV joint and outer CV joint. In the following, we will explore the differences between inner and outer CV joints , their functions, and some common characteristics.

I. Inner CV Joints

Inner CV joints, also known as plunging joints, connect the drive shafts to the transmission system. They are positioned closer to the center of the vehicle, near the engine. Here are some key features and functions of inner CV joints:

1. Function:

   a. The inner CV joints transmit the torque and rotational force from the transmission to the axle shafts.

   b. As the suspension moves up and down, the inner CV joints allow the drive shafts to adjust in length, accommodating the vehicle's suspension travel.

2. Construction:

   a. Inner CV joints consist of an inner race, balls, and an outer race. They have a splined shaft that connects to the transmission output shaft.

   b. The inner races of the CV joints are typically made of hardened steel, ensuring durability under high torque and rotational forces.

3. Movement Capability:

   a. Inner CV joints have a limited range of motion due to their location and connection to the transmission system.

   b. They usually do not undergo as much movement or stress as outer CV joints, as they operate within narrower angles.

II. Outer CV Joints

Outer CV joints, also known as fixed joints, are positioned at the outer part of the axle shafts, close to the wheels. They have distinct features and perform different functions compared to inner CV joints:

1. Function:

   a. Outer CV joints transfer torque and rotational force from the axle shafts to the wheels, enabling the wheels to turn at different angles.

   b. They provide the necessary flexibility for the wheels to steer left or right, allowing the vehicle to navigate corners and turn smoothly.

2. Construction:

   a. Outer CV joints are generally larger and more robust than inner CV joints. They are exposed to harsher operating conditions due to their proximity to the wheels.

   b. The outer CV joint assembly includes an outer race, balls, an inner race, and a protective boot, which is designed to prevent dirt and contaminants from entering the joint.

3. Movement Capability:

   a. Outer CV joints have a higher range of motion as they are responsible for accommodating the steering movement of the wheels.

   b. They are subjected to more significant stress, higher angles, and constant changes in torque during steering maneuvers.

Inner and Outer CV Joints Play Distinct Functions

In summary, inner and outer CV joints play distinct roles in the drivetrain system of a vehicle. While inner CV joints handle torque transmission from the transmission to the axle shafts with limited movement, outer CV joints facilitate the steering function, allowing the wheels to turn and navigate corners smoothly. Understanding the differences between these two types of CV joints is essential for efficient troubleshooting, maintenance, and repair of the drivetrain system.