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transmission shafts

Understanding Transmission Shafts: Types, Materials, Design, and Manufacture

Shafts are versatile engine components with varying applications across industrial manufacturing, consumer products, transportation, and mining industries. Transmission shafts are one of the commonly used shafts.

Transmission shafts have a circular cross-section and are responsible for transferring power or motion within engines or machines. Transmission shafts transfer power from one part producing power to another which receives it. Hence, transmission shafts are core to all rotating machinery.

This guide provides an in-depth discussion of transmission shafts meaning, types, manufacturing processes, and materials used. You will also learn helpful transmission shaft design considerations by reading to the end. Let’s get to it!

Introduction to Transmission Shafts

transmission shafts

Even though power can be generated in several ways, it can be challenging in cases where it is required with perfect amount and direction. As a result, transmission shafts are used in automobiles and other rotating machinery. Transmission shafts are essential machine parts in different mechanical transmissions, especially cars. They are the axles that keep the gears on a vehicle in position and transmit power through the gearbox.

The transmission shaft can be automatic or manual depending on the engine configuration. The design and specification of the transmission shaft play a pivotal role in the layout of the vehicle’s transmission. An automatic transmission employs the planetary gear set to produce varying gear ratios, while a manual transmission works with various gears to the drive shaft.

How Does a Transmission Shaft Work?

how does a car transmission shaft work
How Does a Car Transmission Shaft Work

Transmission shafts often function within manual transmission gearboxes—the transmission shaft transfers the automobile engine’s high output to the wheels. Similarly, the transmission shaft regulates the workable speed during this energy transfer, making it compatible. The gearbox achieves these operations through the complex positioning of the transmission shafts and gear.

Bearings support transmission shafts in machinery as they rotate machine elements like flywheels and pulleys to transmit the torque that the engine needs.

The engine’s crankshaft rotates and generates power, which must pass through the transmission shaft to the wheel. The input shaft is the first component to receive the generated force, and it can be engaged and disengaged through a clutch. The input shaft lies parallel to the output shaft in a rear-wheel drive to form a single component known as the main transmission shaft.

Basic Components of a Transmission Shaft

car transmission shaft system
Car Transmission Shaft System

The transmission shaft is an integral part of a vehicle’s powertrain. It comprises different components, including:

  • Main Case: This is the central housing, usually made with aluminum, steel, or plastic, covering and supporting the transmission shaft and its components. The main case ensures the transmission assembly’s structural integrity.
  • Bearings: Bearings offer support and aid the transmission shaft’s rotation. Bearings facilitate the smooth rotation of the shaft by reducing friction between the moving parts.
  • Bearing Housing: The bearing housing is a vital shaft component that supports and shields the bearings from damage. The housing ensures proper transmission shaft alignment and support by providing a stable and secure location for the bearings.
  • Caps: Caps are enclosures that prevent the gears or bearing from contaminants like dirt, water, and other elements that could cause potential damage to
  • Covers: The covers are additional protective layers that shield the gears and differential housing from dirt and moisture penetration.

Types of Transmission Shafts

Transmission shafts are available in different types, each with a distinct purpose. Here are the commonly used types of transmission shafts:

Main Shaft

main shaft

The main shaft or output shaft is the primary shaft of the gearbox that receives or absorbs the power from the engine. It works by transferring power from the engine to other engine components, such as the gears in the gearbox. It extends from the engine block to the transmission. The main shaft transmits torque and rotational motion to the layshaft.

The main shaft comprises two different shafts, even though it appears as one shaft. A small bearing from the input shaft’s rear supports the front of the main shaft. The main shaft provides a vehicle’s required torque by rotating at different speeds. The main shaft is splined; hence, the synchronizer or gear spins for engagement and disengagement.

Counter Shaft

counter shaft
Counter Shaft

The counter shaft has a parallel orientation to the main shaft, with the input shaft forcing it through a pinion gear. It transfers motion from the primary shaft to the required area. The transmission gears are permanently joined to the countershaft and spin with it in a typical manual transmission design.

In front-wheel drive cars, the input and countershaft are the same, and the car possesses a clutch mechanism that joins it with the engine and shifts power to the main shaft through the gear.

Idler Shaft

idler shaft
Idler Shaft

An idler shaft, also called the reverse idler shaft, is a small plain shaft responsible for reversing the idler gear. As its name implies, it doesn’t partake in torque increase and speed reduction. Hence, it is not mounted directly with the output shaft or the engine. The idler comes with idler gears that mate with gears on both the counter shaft and main shaft.

The primary function of the idler shaft is to reverse the gear’s direction. In other words, it switches the direction of the rotation. An idler shaft supports rotating elements in transmissions like sprockets, gears, and pulleys.

Propeller Shaft

The propeller shaft, also known as drive shafts transfers power from the transmission or gearbox to the differentials and the wheels in a vehicle. The universal joints are connected to both ends of the propeller shaft to facilitate the suspension’s movement.

The drive shaft in the rear wheels layout is a single, long shaft that rotates and transmits power to the rear axle. Meanwhile, the half shaft or drive axle transmits power from the transmission to the front wheels in front-wheel drive cars.

Cardan Shaft

The cardan shaft often comprises two universal joints linked by an intermediate shaft. This shaft facilitates angular misalignment between the connected shafts since they are at different angles and are not in a straight line.

Materials Used in Transmission Shafts

A shaft and gear have tooth-like structures that help to connect them for continuous transfer of rotational power. Engineers often use shafts and gears of different measurements in matching order to generate varying speeds and forces. Mild steel is suitable for manufacturing shafts, while alloy steel, such as nickel, offers more strength.

Materials used in producing transmission shafts must offer specific properties such as high strength and good machinability for efficiency. Typical transmission shaft materials include:


Manufacturers often use alloy steels like nickel-chromium-molybdenum alloys such as 4340 or 4140 to make transmission shafts. These alloy steels are cost-effective and offer a good balance of strength and toughness required for the application. More importantly, steel transmission shafts are compatible with heat treatment processes to enhance strength and hardness.


Aluminum alloys are another suitable material for making transmission shafts. Engineers often use 6061 and 7075 aluminum alloys in lightweight applications since aluminum is lighter than steel. As such, manufacturers in the automotive sector often utilize these aluminum alloys as an alternative to steel to achieve overall weight reduction in automobiles. However, aluminum alloys are not advisable for high-torque applications since they have lower strength than steel.


Titanium is a popular metal with a remarkable strength-to-weight ratio. Hence, engineers often employ them in heavy-duty and high-end applications. Titanium’s excellent strength properties and corrosion resistance make it a suitable material for transmission shafts. Nevertheless, it is costlier than aluminum and steel materials.

Manufacturing Processes of Transmission Shafts

Manufacturers and product engineers often manufacture transmission shafts using processes like mold designing, CNC machining, and rapid prototyping. Here is a detailed explanation of the manufacturing processes:


Molding is a manufacturing technique that molds or shapes molten material through a fixed frame. The mold usually has a cavity made with metal where the hot liquid metal, plastic, or ceramic material flows through. However, you have to construct the mold according to the dimensions of the preferred end products.

CNC Machining

CNC machining comprises different processes, such as milling, turning, boring, and grinding. CNC turning is the most commonly used CNC machining process. It is best used for machining cylindrical components such as the transmission shaft. CNC turning involves removing excess material from rotating workpiece materials fastened to chucks. The process uses different machine tools to cut material from the cylindrical workpiece in a controlled manner, providing the desired dimensions and surface finish.

Drill bits are used to make holes of desired measurements through the center of the material. Then, the machinist uses a mill to make a hole to create a channel for lubricant passage during its operation. A gear shaper machine is used to shape the inner teeth, each one different from the other. After the CNC machine cuts the external teeth, it would be best to ensure they align nicely.

Heat Treatment

Machined transmission shafts are compatible with heat treatment procedures like quenching and tempering. It helps to increase the shaft’s strength, hardness, and toughness, preventing fatigue cracks. However, the material type and required mechanical properties determine the ideal heat treatment process for manufactured transmission shafts.

Surface Finishing

Manufacturers often use surface finishing treatments such as polishing and grinding when manufacturing transmission shafts. These surface finishes help smoothen the surface of transmission shafts and ensure dimensional accuracy. Besides, surface finishes help mitigate friction and wear in transmission shafts, improving their overall performance.

Design Considerations for Transmission Shafts

transmission shafts design
Transmission Shafts Design

There are various factors to consider for effective transmission shaft design. Here are some of them:

Choose the Appropriate Material

Choosing the appropriate material for your transmission shafts ensures peak performance, longer lifespan, and reliability. It would be best to use materials according to the application’s weight, strength, toughness, and cost requirements. Aluminum, titanium, steel alloys, and composites are typical materials that manufacturers employ in transmission shaft design.

Examine the Torque and Power Transmission

Examining the maximum torque and power transmission that the transmission shaft will have to transmit is crucial. This factor helps determine the ideal material, overall design, and diameter for the transmission shaft to ensure optimal performance without failure. Failure to consider these variables will result in transmission shaft failure.

Torsional Strength

When designing your transmission shaft, it is essential to ensure sufficient strength to withstand rotational forces without deformation. Manufacturing transmission shafts with good torsional strength helps maintain the integrity of the shafts when operating under heavy loads.

Surface Finish

Surface finishing is critical to transmission shaft design because it helps minimize friction and wear, ensuring its extended lifespan. Giving a transmission shaft a smooth surface improves its lubricity and overall efficiency. Therefore, consider using a compatible surface treatment for your machined transmission shafts to achieve the best results. Common surface treatments include chrome plating or nitriding.

Custom Transmission Shaft for Your Requirement

at machining

Custom transmission shafts have distinct features that enable them to provide more power and torque transfer and regulation in automobiles. They usually offer higher capacity performance and smooth operation that ensures adequate transmission. These custom transmission shafts are built in ways that match the requirements of the intended purposes.

AT-Machining provides transmission shafts suitable for high-performance applications. We offer lightweight and extremely strong transmission shafts. We leverage our sophisticated CNC machines to produce quality transmission shafts for high-precision engineering tasks.

As a top manufacturer of custom machined parts, prototypes, and industrial products, trust us to deliver custom transmission shafts that meet your requirements. Our experienced professionals pay attention to detail and offer expert advice about your project. Don’t hesitate to Contact us Now, and let us handle your shaft machining projects!


Transmission shafts are pivotal in power and torque transfer from the engine to different parts of machines or automobiles. These components ensure optimal performance of motors and machinery due to their ability to generate and regulate torque and rotational forces.

We have explored transmission everything you need to know about transmission shafts. Understanding the types of transmission shafts, the materials and processes used to manufacture them, and practical design tips help to achieve the best results.

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