How Does an Automatic Transmission Work?

Automatic transmissions are by far the most popular transmissions for vehicles. In fact, automatic transmissions are now so ubiquitous that many people don’t even know how to drive a manual transmission vehicle. But this wasn’t always the case. In the past, all vehicles were made with manual transmissions, but as technology advanced, the automatic transmission became more popular since it makes driving easier.

What Is a Transmission?

The transmission is a series of gears and other mechanical components that work together to transmit power from a vehicle’s engine to the drive axles, which then turn the wheels. Without the transmission, all of the power from the engine would never make it to the wheels. The gears in the transmission need to be shifted to the proper gear ratios according to the vehicle’s speed.

How Are Automatic and Manual Transmissions Different?

Automatic transmissions have some key components that manual ones don’t. The main difference, on the most basic level, is that with a manual transmission the driver is involved in shifting gears. In an automatic transmission, there are mechanical components that shift for the driver.

How Automatic Transmissions Work

Automatic transmissions are complicated pieces of equipment. And there are actually several different types of automatic transmissions and many semi-automatic transmissions, as well as new updates on designs and models.

In an attempt to keep things simple, we’ll be discussing a traditional automatic transmission that uses a torque converter and fluid to transfer power instead of a clutch. In manual transmissions, a clutch is used to transfer power from the engine to the transmission via friction. A torque converter uses transmission fluid to transfer the power of the engine to the rest of the transmission via the spinning parts within the torque converter.

Once the power of the engine is transferred through the torque converter, it goes through a series of other parts in the transmission that work together to get power to the wheels.

  • Transmission Pump

The transmission pump on most models of transmissions is located between the torque converter and the planetary gearset. It pressurizes transmission fluid and pumps it through the rest of the transmission.

The planetary gearset is a system of gears that work together to change the torque multiplication. This in turn affects the speed of the vehicle. When a vehicle shifts gears, a different combination of gears within the planetary gearset turns.

  • Clutches and Bands

Clutches and bands are implemented in the transmission in order to change gears. The bands are usually metal bands placed around certain engine parts that will cinch tight when a certain process is needed. Clutches work with pressure applied by transmission fluid and springs. They also work to engage and disengage power to the areas of the transmission that actually drive the wheels.

  • Valve Body

The valve body directs fluid to the various components of the transmission. It is sometimes run electronically, especially in modern transmissions. The valve body is made up of many different passageways and valves. When a gear is selected, certain valves will function providing power to the right gears.

  • Final Drive

The final drive provides a final gear reduction, which applies multiplied torque to the driving axles.                                                                                                                                                                

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