Hand on a car automatic transmission

What is An Automatic Transmission & How Does It Work?

A “transmission” is simply the name given to the device that connects the engine to the wheels. It is a device designed for cars that changes the gear size in the car to more efficiently use engine power. In simple terms, it allows us to convert the engine power output to the wheels.


A car transmission consists of gears that are used to transfer the rotational motion of one shaft to another. They come in two main types, automatic transmissions, and manual transmissions.

Automatic Transmission

An “automatic transmission” is one where the driver doesn’t have to manually shift gears. Automatic car transmissions are different from conventional manual transmissions. Both are used in automobiles; however, there are some key differences between the two. Automatic transmissions use hydraulic fluid to engage the correct gear and maintain optimal RPM. They are found in most modern vehicles today.


Manual transmissions are still very popular because they offer better fuel economy and superior control. However, many people find themselves preferring the convenience of automatic transmissions over manual ones. You can check out our Transmission Guide for more information on the difference between manual and automatic transmissions.

Automatic Transmission Basics

    • Automatic transmission parts include: planetary gears, clutches, fluid couplings, and bearings
    • Six-speed automatic transmissions are the most common
    • Older cars may have four or five automatic gears
    • The torque converter performs the function that a mechanical clutch traditionally does by facilitating gear changes
    • You can get a transmission inspection to make sure your transmission is working smoothly and efficiently.

    Do Automatic Cars Have a Clutch?

    Yes, the mechanism used in all cars to change gears is a clutch. It facilitates gear changes similarly to how a manual clutch would through the use of the torque converter.


    However, there is no clutch pedal in an automatic transmission. The driver relies on the car to automatically change gears, rather than using the clutch pedal to make the shift, thus the term, “automatic transmission.” 

    How Does an Automatic Transmission Work?


      • Uses five to ten gears to reach a wide range of speeds
      • The gearbox chooses the right gear based on the speed of the car
      • In an automatic transmission, it disconnects the engine from the wheels automatically as it changes gears, by activating the clutch
      • The clutch causes the car to shift gears smoothly without any hesitation, compared to manual transmissions which rely on the reaction of the driver and the clutch pedal

      Advantages of an Automatic Transmission


        • Ability to drive without needing to manually use clutch
        • Easier to control at low speeds and in stop-start traffic
        • Smoother transition between gears
        • Less likely to accidentally grind gears and cause transmission to fail. In the case of a transmission failure, you may need to visit an auto transmission repair shop.
        • Less likely to stall

        Have Questions About Automatic Transmission?

        By understanding what an automatic transmission is, you’ll have a better understanding of how your automatic car works or if purchasing an automatic transmission car is right for you.


        If you have more questions regarding transmissions, you can reach out to us or visit transmission shops Chattanooga to repair any transmission issues.