Types of Gearbox in Cars and Its Functions Explained

A vehicle's gearbox is also called a transmission system and uses gears, actuating parts and shafts to transfer power from the engine to the wheels. Simply put, it is a box containing gears.

You can find gearboxes in everything from heavy machinery and turbines to automobiles. This blog will focus on the different types of gearboxes in automobiles.

It is the gearbox that helps a driver maximise and minimise torque. In automobiles, a gearbox is a metallic box surrounding various combinations of gears. Each gear is of a different size, with the first one being the largest and providing the maximum torque and minimum speed.

A driver can select different gears by using a movable gear selector. He or she can select a gear that changes the torque output and speed of a car’s motor. When the configuration of gears is changed, an output shaft connected to the gearbox changes its output torque and speed.

A car requires different levels of torque at different conditions to function well. For example, when a vehicle is climbing up a hill, it requires more torque because of a higher friction load, which demands more fuel consumption. However, it requires less torque when it has gained sufficient velocity. In such a situation, a driver can reduce fuel consumption by reducing the torque.

A car's gearbox is essential in transmitting the available power from the engine to the wheels, thus creating movement in a vehicle. It achieves this through a set of gears that can be engaged to alter the car's speed and torque in motion. The gearbox's roles include raising the torque level while enabling the car to reverse and offering a neutral position.

The gears are arranged in various combinations, allowing the gearbox to have multiple speeds while achieving maximum engine power. Higher gears, incorporating smaller cogs at the rear wheel, produce less force at a faster speed and are used when descending a slope or where less power is needed. On the other hand, higher gears are intended for smooth and rapid driving, such as on the highways.

Thus, it is crucial to have an efficient manner of varying speed and torque to enhance vehicle performance and fuel efficiency, hence the importance of a gearbox.

Car gearboxes, often referred to as transmissions, are available in different types because each type caters to the specific needs of drivers and vehicles. Indeed, the primary division is between manual and automatic, while several subtypes exist in the latter group. 

These are the normal torque converter, the CVT (the continuously variable transmission), the AMT (the automatic manual transmission), and the splendid DCT (Dual clutch transmission).

1. Manual Transmission

This gearbox is also referred to as a stick-shift unit or standard transmission. The driver must manually shift the gears with a clutch and movable gear selector. Manual transmission is present in most vehicles due to its low costs.

Features: Sliding gear transmission, constant mesh transmission, and pre-selector transmission are some different types of manual gearboxes. Given are some important points about these gearboxes.

• You can find sliding gear transmissions in old models of cars. Today, vehicles no longer use them.
• Constant-mesh transmission ensures that the cluster gear, drive gear and main shaft gear remain in constant motion. You can use a dog clutch to lock these gears.
• Pre-selector transmission system uses a planetary gear system to pre-determine gear ratios with a small lever on the steering column. Then, the driver uses a foot pedal to call up a pre-set gear, and this process disengages the previous gear when the new gear engages.

How It Is Useful: The manual transmission gearbox lets a driver control the gears fully. It allows the driver to use his skills in choosing suitable gear to save fuel. It also helps him to make progress quickly.

2. DCT (Dual Clutch Transmissions) Automatic

More people are choosing to use dual clutch automatic transmission systems, so it has become a common gearbox for diesel and petrol cars. There are two clutches in these types of gearboxes—one for the odd-numbered gears and another for the even-numbered gears.

Features: Listed below are the features of this gearbox:

• As this transmission system can pre-determine the next gear, the shifts happen quickly.
• There are mainly two types of DCT automatic transmission systems—wet multi-plate clutches and dry multi-plate clutches.
• Engineers have developed wet-clutch DCT for engines with a high torque output. On the other hand, a dry-clutch DCT is ideal for smaller engines with a lower torque output.

How It Is Useful: This gearbox is present in many performance cars where the gear changes are nearly indistinguishable. In addition, if the car has a dry-clutch DCT, there will be no fluid pumping losses resulting in greater fuel efficiency.

3. Torque Convertor Automatic

This is an automatic transmission system where the driver does not shift gears physically. It is a widely used gearbox called a torque converter that enables the car to stop even when the engine is functioning.

Features: The features of a torque converter automatic gearbox are as follows:

• This transmission system has the capability to multiply the torque even during low output rotational speed.
• A torque converter has a stator which changes the drive characteristics to facilitate increased torque output.
• Usually, large-capacity engines that produce a very high torque output use this type of gearbox. In addition, this transmission system is less likely to fail as they have a better structure.

How It Is Useful: The most important benefit of this transmission system is that it facilitates smooth acceleration from low speeds and good responsiveness even at low engine revs.

4. AMT (Automated Manual Transmission)

This manual gearbox has an electronically or hydraulically controlled actuator that shifts the gears automatically. It uses a regular clutch, gear configuration, sensors, processors, actuators, and pneumatics.

Features: The following are some important features:

• Vehicle speed and throttle input determine the gear shifts.
• This transmission system focuses on driving convenience rather than comfort.
• Note that AMTs are reasonably priced. They are more affordable than conventional automatic transmission systems.

How It Is Useful: An important advantage of this type of gearbox is its high fuel efficiency. Moreover, it ensures high fuel mileage if you are travelling long distances.

5. CVT (Continuously Variable Transmission) Automatic

This automatic gearbox is also known as a pulley or step-less transmission system. Continuously Variable Transmission gearboxes do not depend on torque for functioning. Instead, it uses gear ratios for transferring for powering up the vehicle.

Features: The following are some important features of these gearboxes:

• CVTs have a cone with a band around it and an axle in the place of a gear. You can move the band up and down to alter the length and gear ratio.
• This automatic transmission system offers infinitely variable gear ratios, improving fuel efficiency and a vehicle's performance.

How It Is Useful: A CVT is beneficial for hybrid cars that use this transmission system to effectively balance the workload between an electric motor and a petrol engine. This relatively new system is undergoing many improvements, so the next versions could likely be considerably better.

Given below are the main points of how the gearbox functions:

• The constant-mesh gearbox has a drive shaft which remains connected to all gears. It is the layshaft that has the gear mounted upon it.
• There are many gears in the layshaft that are well-arranged with these gears.
• There is no direct connection between the gears and the main shaft. The gears can rotate around it freely.
• There are dog clutches that help in engaging the gear. In addition, they are splined to the primary shaft and help rotate. Furthermore, these dog clutches contain frictional material that enables them to connect with each gear on the main shaft.
• Now, when the driver pushes the gear stick, the interconnected dog clutch connects with a selected gear after receiving a signal from the selector fork. Consequently, both the clutch and the gear start rotating as per the selected gear's speed.