Universal Joint: Working, Parts, Types, Uses [PDF]

In this article, I shall explain to you about universal joints their working, types, parts, and uses. I have also provided a PDF at the end.

What is a universal Joint?

A universal joint, often referred to as a Cardan joint or hook joint, is the oldest type of flexible coupling and is widely used in automobiles and trucks. It serves to connect two shafts at an angle to transmit torque.

In the vehicle’s transmission system, the universal joint plays a crucial role when the output shaft of the gearbox, the propeller shaft, and the differential pinion shaft are not aligned in one line. This joint allows torque transmission at varying angles, accommodating changes as the vehicle moves. Known for its simplicity and versatility, the universal joint is suitable for various applications, boasting unique features.

Purpose of Universal Joint

The purpose of a universal joint becomes evident when a car traverses uneven terrain, causing the differential to rise and fall. Simultaneously, the propeller shaft changes angle as it rotates.

In such circumstances, these joints facilitate adjustments in the propeller shaft angle without affecting the transmission. Without a universal joint, a direct connection from the gearbox to the differential would result in a failed connection during the rear axle’s rise and fall. This failure occurs because the connection lacks flexibility in the absence of a universal joint.

What is universal joint
universal joint uses

Parts of Universal Joint

The universal joint comprises the following parts:

  • Driving Yoke and Driven Yoke
  • Spider

Driving Yoke and Driven Yoke

  • The joint is composed of two yokes, namely the driving yoke and the driven yoke.


  • The yokes are linked through a cross-shaped intermediate component known as the spider.
  • This arrangement allows the shaft to rotate at various angles.
  • When the shaft is connected in a straight line, the input shaft rotates the cross, subsequently turning the output shaft.
  • It is evident that both the input and output shafts rotate at the same speed.

Working of universal joint

The universal joint operates by incorporating a driving yoke labeled ‘1,’ which connects to the main gearbox shaft. On the opposite end, there is a driven yoke ‘3’ linked to the propeller shaft.

These yokes are joined by a crossed spider ‘2,’ where the four arms of the spider are termed trunnions.

parts of universal joint
universal joint parts

When the driving shaft rotates, it imparts rotation to the driven shaft. Concurrently, the universal joint facilitates angular motion. Consequently, power is transmitted from the gearbox to the propeller shaft at an angle.

Universal joints serve to establish a flexible connection between two rigid shafts positioned at an angle to each other. They enable power transmission not only at an angle but also while this angle undergoes constant variation.

The function of Universal Joint

The universal joint performs the following functions

  • It connects two shafts with intersecting axles.
  • It allows one shaft to rotate about its axis while being influenced by another shaft rotating about its axis.
  • It facilitates power transmission not only at an angle but also while this angle undergoes constant changes.

Types of Universal joint

There are three main types of universal joints:

Cross-Type Universal Joint:

This joint features two Y-shaped yokes and a crosspiece (spider). One yoke attaches to the driving shaft, and the other connects to the driven shaft. The crosspiece, with four arms (trunnion), connects to both ends of the yokes. Bearings on each arm enable the yoke to move around the trunnion, allowing the driving and driven shafts to operate at an angle.

Ball Trunnion Type Universal Joint:

Combining universal and slip joints in one assembly, it includes a ball-type head fastened to one end of the propeller or drive shaft. A pin or cross shaft, forming a ‘T’ shape, passes through this end with two steel balls fitted firmly. This joint facilitates rotational motion through the ball and the pin, allowing axial movement of the balls. It is also known as a variable velocity joint.

Constant Velocity Type Universal Joint

This type enables both driving and driven shafts to move at a constant velocity. The joints act at the same angle, making them suitable for front-wheel (axle) drive vehicles. Using these joints is crucial in front-wheel drive vehicles to prevent speed variation between the driving and driven shafts, which could lead to steering system difficulties and excessive tire wear.

Universal Joint Diagram
Types of universal joint

Advantages of Universal Joint

  • Exhibits greater elastic properties than knuckle joints.
  • Facilitates torque transmission between angularly misaligned shafts.
  • Cost-effective and easy to assemble and dismantle.
  • Achieves high torque transmission efficiency.
  • Allows angular displacement, distinguishing it from other types.

Disadvantages of Universal Joint

  • May experience wear and tear if not properly lubricated.
  • Requires regular maintenance to prevent wear.
  • Can cause unstable motion.
  • Lacks the capacity to support axial misalignment.

Applications of Universal Joint

  • Positive Mechanical Joints:
    • Commonly used to connect shafts, especially in the propeller shafts of rear-wheel-drive cars, for transmitting motion, power, or both.
  • Thermoplastic Body Member Joints:
    • Applied in light industrial settings due to their advantages, including self-lubrication, lightweight construction, low reactivity, corrosion resistance, and the ability to operate at high speeds.
  • Versatile Applications:
    • Widely used in airplanes, control mechanisms, electronics, instrumentation, medical and optical instruments, armaments, radios, sewing machines, textile machinery, and tool drives.


In conclusion, this article comprehensively explores universal joints, covering their working principles, types, parts, and applications. The universal joint’s pivotal role in transmitting torque between angularly misaligned shafts is highlighted, emphasizing its simplicity and versatility. A downloadable PDF is provided for further reference, making this resource valuable for understanding and applying universal joint concepts.

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