What Is an Automatic Car Transmission and How Does It Work?

March 24, 2023

Cars with automatic transmissions have become increasingly popular due to their ease of use and convenience. As of 2022, nearly 97% of cars used in Australia are automatic. Here, we will discuss everything about automatic car transmissions and the modern technology behind them. Read on to learn more!

What Is an Automatic Car?

What Is An Automatic Car

Automatic cars have automated transmissions, eliminating the need for drivers to shift gears manually. Gearboxes, commonly known as transmissions, facilitate a car engine’s directional force and velocity.

Special sensors allow an automatic transmission system to adjust gear ratios while driving the vehicle. These sensors tell when internal oil pressure needs to be used. Automatic car transmissions only have two pedals. The left pedal is for acceleration, and the right pedal is for slowing down.

How Do Automatic Car Transmissions Work?

How Do Automatic Car Transmissions Work?

Automatic transmissions are the most popular transmission system used in cars today. They let you control your vehicle’s speed transmission and allow engines to run optimally for better fuel economy and performance. Automatic transmissions use various components to provide smooth shifting, torque transfer, and more.

The first component of automatic car transmissions is a set of gears designed to work together. Each gear has its ratio between engine revolutions per minute (RPM) and wheel revolutions per minute (RPM).

As the driver changes gears, these ratios adjust to provide the best possible performance for their desired outcome. For example, shifting from first gear to second gear will slightly increase the ratio as well as the acceleration.

Aside from gears, here are the several parts that help automatic car transmissions function properly:

  • Pumps: Supply fluid power to shift the transmission’s gear valves and control how much fluid pressure is applied in each instance
  • Valves: Reduce power loss and engine load
  • Clutches: Provide smooth shifting between gears
  • Brakes: Slow down or stop the vehicle

The overdrive mode is another feature of most modern automatic car transmissions. It can be triggered by manually pushing an overdrive button or engaging an overdrive switch on the dashboard or shifter area. The overdrive mode has several functions:

  • It helps drivers cruise the highway by keeping the engine from revving too high at lower speeds
  • It gives engines extra power when driving past roads and steep inclines

Some automatics include a third gear. Third gears give drivers extra power with less speed and prevent the transmission from shifting to a higher gear. They are most useful when going uphill or downhill, pulling heavy objects, and driving on ice or sand.

However, once your engine reaches its RPM limit, the engine will automatically change to a different gear. This helps avoid any potential damage caused by excessive stress on the engine parts.

What Is the Difference Between Manual And Automatic Car Transmissions?

Basically, manual and automatic transmissions differ in how they change gear ratios as the car moves. Manual transmissions require the driver’s input to shift gears, while automatic transmission use hydraulic power.

Manual Transmission’s Gears

Depressing the clutch pedal in a manual transmission interrupts the power flowing from the engine to the transmission. The manual transmission has six gears:

  • Neutral
  • First gear – 3.166:1
  • Second gear: 1.882:1
  • Third gear: 1.296:1
  • Fourth gear – 0.972:1
  • Fifth gear – 0.78:1

Each gear ratio optimises engine power and torque output for different engine speeds. So, you should manually upshift or downshift using the clutch pedal and shifter lever when accelerating or decelerating at speeds not optimal for the gears.

Automatic Transmission’s Gears

An automatic transmission utilises a complex planetary gear set, which is composed of three main components:

  • a sun gear
  • a planet carrier assembly with three planet gears
  • an outer ring gear

These parts work together to provide the necessary power output for acceleration or deceleration.

The input shaft on the device connects to the engine and its sun gear. The planet carrier assembly remains motionless; this then engages with the outer ring gear linked to an output shaft. The output shaft provides power to your wheels as they turn around in a cycle.

The “automatic” transmission allows your car’s computer to move its gear according to the vehicle’s speed without the driver’s “manual” intervention. It can automatically switch gears based on driving conditions and needs rather than relying on user input. This feature provides an ease to drivers behind the wheel.

Components of Automatic Transmission

Components of Automatic Transmission

The automatic transmission is a complex assembly of components that allow a vehicle to transition between gears when changing speed. These components help drivers diagnose issues in their transmission and make informed decisions about maintenance and repairs.

Transmission Casing

The transmission casing is the house of the entire transmission system. It holds all the internal components in place and keeps them safe from dirt and debris. The transmission casing also supports the drive shafts and other components.

Torque Converter

The torque converter transfers mechanical energy from the engine to the transmission through a pressurised hydraulic fluid. The fluid spins two sets of clutch plates in an enclosed casing. The torque generated depends on how much pressure is applied to each set of clutch plates. So, you must use proper settings to get the most out of this component.

Planetary Gears

Planetary gears help transfer power from one gear ratio to another and provide smoother shifts than direct drive systems can offer.

Brake Bands and Clutches

Brake bands and clutches are two separate but complementary functions in an automatic transmission system. The brake bands are used to slow motion or stop the vehicle completely. Clutches disengage and engage gears without interrupting the engine’s power delivery or torque output.

Oil Pump

An oil pump circulates oil throughout an automatic transmission system to keep things lubricated and free from excessive wear and tear. It supplies clean oil whenever necessary to keep all parts functional. Having a defective oil pump can cause overheating and failure of the transmission due to friction between moving parts.

Output Shaft

The output shaft connects the transmission system to the rest of your car’s driveline (such as axles). It takes power from inside the transmission casing and sends it outwards to other components in need. Turning the drive shaft will move the car forward.

5 Types of Automatic Car Transmissions

Types of Automatic Car Transmissions

Here are the various types of automatic transmissions found in modern and older vehicles:

1. Automated Manual Transmission (AMT)

An automated manual transmission is also known as semi-automatic transmission or clutchless manual transmission. It is an automatic gearbox that uses standard components like a gear configuration and regular clutch. However, it still relies on sensors, actuators, processors, and pneumatics to replicate the actions usually performed by manually shifting gears.

Automated manual transmissions are renowned for their jerky engine performance when travelling at low speeds and hard acceleration capabilities. They are fuel-efficient, great for long drives, and have higher mileage expectancy.

2. Intelligent Manual Transmission (iMT)

Intelligent manual transmission is a practical alternative to expensive automatic gearbox systems. It offers the convenience of an automatic transmission while still providing traditional manual control. So, they make popular choices for those who want the simplicity and comfort of an auto gearbox.

IMT is more affordable and present in a range of vehicles like Kia and Honda than other types of automatic transmissions. They also have improved fuel efficiency brought by manual shifting.

The intelligent manual transmission is a revolutionary technology that eliminates the need for a clutch pedal. The system automatically controls the clutch, and gear shifting requires manual operation with a traditional gear stick lever.

Cars with intelligent manual transmissions are easier to drive than those with automated manual transmissions. The performance of IMT vehicles is superior to that of vehicles fitted with AMT. This is because gear shifting is seamless, without sudden jolts or jerks.

3. Continuously Variable Transmission (CVT)

Continuously variable transmission is another type of automatic transmission with an infinite number of gear ratios. This new feature provides an optimal power range to the vehicle’s engine regardless of speed. CVT cars offer improved fuel economy and smoother acceleration than traditional automatic transmissions.

Constant variable transmission is an efficient technology that maintains consistent engine revolutions per minute (RPM) during acceleration or deceleration. This is done by continuously adjusting the gear ratio to let the engine run at optimal RPMs.

4. Dual Clutch Transmissions (DCT)

The dual-clutch transmission is also called the direct shift gearbox. It is an advanced automatic car technology currently leading the market. This transmission type utilises a twin-clutch system, providing smooth shifting between gears for a comfortable driving experience.

The latest generation of cars with DCT offers some of the quickest and most precise gear shifts available. They also provide reliable performance and extraordinary fuel efficiency.

5. Torque Converter

Torque converters are the oldest form of automatic transmission. At its core, it utilises a planetary gear system with an impeller and turbine. This combination enables torque converters to transition from one gear to another smoothly.

Although it provides a smooth driving experience, it has low fuel efficiency. Nevertheless, most higher-end models now have a torque converter automatic gearbox for a more comfortable ride.

Pros and Cons of Automatic Transmissions

Pros and Cons of Automatic Transmissions

Cars with automatic transmissions have become increasingly popular due to their ease of use and safety features. Here are the pros and cons:


  • Convenience: Cars with automatic transmissions are easier to drive because drivers don’t have to shift gears constantly. This is useful when driving in stop-and-go traffic.
  • Accessibility: Automatic transmissions are an excellent option for people with disabilities who cannot operate a manual transmission.
  • Reduced wear and tear: Automatic transmissions are less prone to wear and tear because it uses a hydraulic system. This system is the equivalent of the manual shifting of gears in manual transmission.
  • Resale value: Automatic vehicles generally have a higher resale value than manual vehicles because of their clutchless feature and convenience.
  • Innovative: Developing new automatic transmission technology, such as continuously variable transmissions (CVT), increases fuel efficiency and reduces maintenance costs.


While automatic transmissions offer convenience and ease of use, they also have drawbacks. Here are some cons of cars with automatic transmissions:

  • Reduced Fuel Efficiency: Automatic transmissions can be less fuel-efficient than manual ones and require more energy. This is because its power source, such as a motor or torque converter, requires additional energy to operate and shift gears.
  • Costly Repairs: Mending automatic transmissions requires technical knowledge and equipment, which can be expensive. Car owners must know the intricacies of this system and possess the right tools to do repairs by themselves.
  • Limited Off-Road Capability: Automatics are less favoured in some off-road driving circumstances because drivers have less control of the vehicle’s speed and torque. Also, automatics are less efficient in traversing slopes, difficult terrains, and steep inclines.
  • Maintenance Issues: Automatic transmissions can be more intricate and challenging to service, and repair costs are typically higher. Any malfunction in one part of the transmission can cause damage to other components.


Why Do People Prefer Driving Automatic?

Automatics are much easier to drive than manual vehicles for some reasons:

  • Drivers don’t have to deal with stop-start pedals during slow-moving traffic
  • Automatics are also considered safer than manuals because of their improved traction control, brake assist, and safety features
  • Automatic require less learning and skill from the driver, making them attractive for novice drivers

Are Automatic Cars More Popular than Manual Cars in Australia?

The decline of sales in manual cars peaked in 2021, which marked the slow death of manual cars. Toyota retailers started dropping manual options for selected cheaper cars. Also, we saw the rise of the automatic Toyota HiLux, the biggest-selling car in 2022.

Are Automatic Cars Good For Beginners?

Driving an automatic car is far simpler than mastering a manual vehicle. They are the most suitable option for beginners whose priority is to get behind the wheel.

Driving a manual car requires the driver to change gears, use a clutch, and press the brake pedals. Automatic cars only require one input from the driver – pressing down on the gas or brake pedal. Also, they are straightforward to drive in congested urban or city roads and do not need manual gearboxes.


We have explored the world of automatic car transmissions and learned about their basic functions, components, and differences from manual transmissions. Again, automatic transmissions use hydraulic fluid, planetary gear sets, and torque converters to shift gears automatically.

They are more expensive but offer greater convenience and accessibility for drivers of all experience levels.

Understanding the basics of fully automatic car transmissions can help you decide if it’s the best for your driving needs. Whether you choose an automatic or manual transmission, always remember to prioritise safety and maintenance to make it last for years.

Upgrade your driving experience with the convenience and ease of automatic car transmission. At Mad Man Motors, we offer a selection of vehicles with automatic transmissions. Contact us today for more information about our fleet!

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