Types of automatic gearbox and how they work
Last updated October 18, 2022
The vast majority of cars use a gearbox to transfer engine power to their wheels. There are two main types of gearboxes used across the industry – manual and automatic. We’ll take a closer look at automatic gearboxes here.
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What is an automatic gearbox?
An automatic gearbox is a car transmission device that can transfer the right amount of power (torque) from the engine to the wheels automatically. This means that the car will change gears correctly with no driver input, which many drivers find makes driving easier.
Why do cars need a gearbox?
Gearboxes are used to balance the engine’s RPM (Revolutions per Minute) and ensure that there is not too much or too little power being transferred to the wheels at any given time. Without a gearbox, a car’s engine would quickly overheat or the vehicle would be unable to reach its specified car engine capacity. Gearboxes also help to reduce unnecessary fuel consumption, as different gears use fuel at different levels – this is because the higher the gear, the lower the revs and the less fuel is required to move the vehicle.
How does an automatic gearbox work?
Inside an automatic gearbox is a torque converter, which is responsible for transferring engine power to the wheels. The torque converter contains a fluid that allows it to multiply the engine's torque, making it possible for the transmission to function properly.
The torque converter is connected to a series of gears known as planetary gearsets. These gears work together to provide different gear ratios, depending on the speed and load of the vehicle.
What is the difference between a manual and an automatic gearbox?
The main difference between a manual gearbox and automatic gearbox is the level of driver input required. Manual transmission uses a clutch to switch gears, with this change triggered by the driver manually moving the gear stick into the correct position. Automatic transmission requires no action from the driver at all and the gear is adjusted automatically based on the engine speed.
If you are planning to purchase a new car, you may be interested to learn that automatics tend to maintain more of their initial value over time than manual equivalents. Don’t forget, you can get a free 30-second car valuation for your current vehicle with webuyanycar.
Types of automatic transmission
There are several types of automatic gearbox used across the car manufacturing industry, each with different features.
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Automated manual gearbox
While automated manual gearboxes are mechanically the same as traditional manuals, the clutch is automatically activated by electric motors whenever a change in gear is needed. These systems allow only Drive and Reverse to be activated via the gearstick and do not feature a clutch pedal.
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Dual-clutch automatic gearbox
A dual-clutch automatic gearbox is similar to an automated manual, featuring electric motors that activate the clutch and gear change. The main difference between the two is that this gearbox features two clutches rather than just one, meaning the vehicle is able to prepare the next gear in advance, leading to quicker gear changes. Dual-clutch gearboxes can mainly be found in performance vehicles.
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Electric car automatic gearbox
Electric cars rarely need a gearbox, as the motors used in place of a traditional engine are comparatively small and mounted close to the wheels. For this reason, EVs generally just feature a lever allowing the driver to switch between Drive and Reverse and are only classed as automatics due to the absence of a clutch pedal.
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Torque converter
While not the most fuel-efficient system, torque converters use hydraulics to change gear, offering an almost seamless switch. These systems often have between 6 and 10 gears and are most commonly fitted to luxury car models.
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IMT
IMT (Intelligent Manual Transmission) is the most affordable automatic gearbox system. This type of gearbox features no clutch pedal and controls the clutch automatically, though gear shifts must be carried out manually using a gear lever.
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CVT automatic gearbox
CVT (Continuous Variable Transmission) gearboxes use a series of belts and cones to continuously identify the most appropriate gear throughout your drive, allowing for a smooth and fuel-efficient driving experience.
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CVT
CVT differs from a CVT automatic as it does not use gears at all. Instead, two pulleys – one connected to the engine, and one connected to the wheels are used to determine when a gear change is needed.