How Does An Automatic Transmission Work?

Chances are you usually jump in your car, turn the key and take off without giving any thought about what makes you able to go. It probably takes a major malfunction before you even think about what is under your hood. However, familiarizing yourself with major automotive components before a break down puts you at a clear advantage when your car conks out.

Nearly all autos have a transmission. (Except for electric cars) It is, quite literally, a gearbox. Your transmission is a metal case that houses gears, bearings, shafts and other parts that send and regulate power from the engine to the wheels. The transmission is what makes you move.

There are two types of transmissions in the automotive world, manual and automatic. In this day and age, automatic transmissions are the most common in cars. Automatic transmissions regulate themselves. They automatically change gears as the vehicle move and changes speed. Now you are probably wondering how that happens. So, how does an automatic transmission work? Let us break it down for you.

Eliminating the Gear Shift and Clutch Pedal

There are two big differences in automatic and manual transmissions. There is no clutch pedal in an automatic transmission. There is also no gearshift. That is because everything is automatic once you put your car in drive.

Your transmission is needed to change the speed ratio between the engine and the wheels of your car. That ratio changes as you increase speed. This requires a shift. An automatic transmission does this by itself. This is because an automatic transmission uses a torque converter instead of a clutch. The torque converter is made of a separate pump and turbine spinning in opposite directions, which allows the engine to spin independently of the transmission.

In addition, a manual transmission locks and unlocks different sets of gears to achieve the various gear ratios. However, the same set of gears is able to produce ALL of the different gear ratios in an automatic transmission. This is possible through the use of a special planetary gear set.

Planetary Gear Set

The automatic nature of an automatic transmission could not be possible without the single gear set known as the compound planetary gear set. It is one single gear set that function as multiple gears. It has one main ring gear that is always the output of the transmission. It also has four other sets of gears that move to spin the tires with the appropriate torque as you accelerate. Various combinations create all of the different gear ratios a transmission can produce. This typically includes four forward gears and one reverse gear.

The gear set is controlled and regulated by a complex hydraulic system. Various bands and clutches control the gears. A gear pump pushes the transmission fluid through the system to keep everything lubricated and moving. A valve called the governor tells the transmission how fast the car is going. It then regulates the movement of shift valves that supply the hydraulic fluids to engage the different gears. The faster the car moves, the faster the governor spins and the wider the valve opens to let fluid through.

It is important to understand how your vehicle works in order to maintain it. Now that you know how an automatic transmission works you can better understand the importance of maintaining it. An automatic transmission is an extremely complex part, so regulate inspection and maintenance are critical to keeping it running.

When automatic transmission problems arise, you want a team of experts on your side. You can trust the professionals at Express Transmissions. If you are in need of transmission repair, call us today at 419-861-8118.