How Does a Transmission Work?

When you get behind the wheel of your car or truck and put it in gear, you expect it to move. Take a closer look at vehicle parts diagrams, and you see that the transmission plays a role in making this happen. It's a complex part with an important job.

Transmission Basics

Your car or truck's transmission is part of its drive train. It's purpose is to transfer power produced by the engine to the wheels. If you've ever been on a multi-speed bicycle and changed the gears, you know that putting it in the wrong gear for the speed you want to go makes it difficult to move. This is also true of a transmission.

Parts of a Transmission

Take a look at a transmission parts diagram and you see how complex this part is. There are clutches and bands, gears, a pump, sensors, a torque converter and valve body. All transmissions also have transmission fluid that lubricates the transmission and keeps it cool. These parts must be present and functioning property for the transmission to do its job. As they age, they become less effective. That's when it's time to replace the worn parts during a transmission rebuild.

Gear Ratios

Transmissions have grooved gears that spin in tandem to create torque needed to move the vehicle. The input and output gears are different sizes, each transmission has several gear ratios. Gear ratios change along with the vehicle's speed, and the way the gears work together make it happen. Transmissions also have selectors that let you reverse direction, park or leave the vehicle running while in neutral.

Manual Transmissions

If you have a vehicle with a manual transmission, you choose the gear by pressing the clutch and moving the gearshift into the appropriate position. Driving a vehicle with a manual transmission requires more skill than those with automatic transmissions, but it gives the driver more control over the speed of the vehicle. Many people who like working on their own cars prefer manual transmissions because they are less complex than automatic transmissions and easier to repair.

Automatic Transmissions

An automatic transmission changes the gear ratios on its own. The automatic transmission fluid inside the case provides pressure that moves the clutches and bands to select the appropriate gear. These transmissions are popular because most people find them easier to drive since they don't have to learn how to engage the clutch to change gears. They're more complex parts, though, which can be more costly to repair when something goes wrong.