Metro Works: Automatic Transmissions

Understanding Automatic Transmissions And How They Work

If you drive a car with an automatic transmission, then you know how easy it is to shift gears. But have you ever wondered what’s actually going on inside the transmission? In this blog post, we will take a closer look at automatic transmissions and break them down into their individual components. We’ll explain how they work and what each part does. So if you’re curious about automatic transmissions, read on!

The automatic transmission is one of the most important components in a car. It’s responsible for shifting gears and transferring power from the engine to the wheels. There are several different parts that make up an automatic transmission, and each one plays an important role in its function. 

Here Is A Breakdown Of The Individual Main Components Of An Automatic Transmission:

  • Pump
  • Planetary Gearset
  • Torque Converter
  • Clutch drums
  • Solenoids & Valve body


The pump in an automatic transmission is responsible for producing the hydraulic pressure inside an automatic transmission. When a pump wears out in the transmission, several things could possibly happen. You could have a loss of pressure causing slipping shifts, delayed engagements or if the pump completely goes, the vehicle would completely stop moving.

Planetary Gearset

A Planetary Gearset is a gear arrangement consisting of three parts: the sun gear, the planet gears and the ring gear. The planet gears are mounted on a carrier and rotate around the sun gear. The ring gear is connected to the housing.

The Planetary Gearset is used in automatic transmissions because it provides numerous speed ratios in a relatively small space. It does this by having the planet gears rotate around the sun gear, while being locked to the housing by the ring gear. This causes the output shaft speed to be slower than input shaft speed when ratio is less than one, and output shaft speed to be faster then input shaft speed when ratio is greater than one. This results in a wide range of possible ratios that an automatic transmission can use.

Torque Converter

Torque Converters are used in automatic transmissions to multiply torque. By doing this, the engine can operate at a lower speed while the transmission is able to provide enough power to drive the car. Inside Torque converters, you have a turbine and an impeller. Sometimes there are planetary gears and some have clutches inside. The turbine is connected to the engine, while the impeller is connected to the transmission. As the turbine turns, it causes the impeller to turn as well. This action creates a fluid coupling between the two parts, which allows for torque multiplication.

There are several benefits that come with using a Torque Converter in an automatic transmission. One benefit is that it helps to improve fuel economy since the engine does not have to work as hard. Another benefit is that it can help to reduce wear and tear on the transmission since it is not being overloaded with too much power. Torque Converters are a vital part of an automatic transmission and can help to improve its overall performance.

Clutch drums

A Clutch drum is a device in an automatic transmission that houses clutches. With hydraulic pressure, the clutches are engaged which in turn holds a section of planetary gears to start driving the gear set. Most transmissions have at least 3 clutch drums, but most newer transmissions have more.

Solenoids & Valve body

A Solenoid is a device used in an automatic transmission that controls fluid flow and pressure within the transmission. The Solenoid is responsible for engaging and disengaging the various clutch packs inside the transmission, as well as regulating the fluid pressure that is necessary for smooth gear operation.

Solenoids are essentially electronic valves that control the flow of hydraulic fluid within the transmission. The Solenoid is controlled by an electrical signal from the vehicle’s computer system. When the Solenoid is energized, it opens a passageway for hydraulic fluid to flow into or out of a particular area in the transmission. This movement of hydraulic fluid can allow the transmission to shift into different gears, or vary the pressure inside the transmission. 

The Valvebody has numerous valves that control pressure, regulate shift timing and shift feel and contains the various solenoids that an electronically controlled transmission has.

The automatic transmission is a complex system with many different components. 

And by understanding how each part works, you can see how it all comes together to create an easy-to-use driving experience. If you have any questions about how automatic transmissions work, call Metro Transmission and we would be happy to answer them for you. 

Metro Transmission

Metro Transmission

The ASE Certified Mechanics at Metro Transmission and Automotive have over 100 years of combined experience. We're a full service, AAA Approved Auto Repair Shop, conveniently located in San Marcos, CA off Highway 78.

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