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Mission - Automatic Transmission |
| edHelper's suggested reading level: | grades 5 to 7 | |
| Flesch-Kincaid grade level: | 12.32 |
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Mission - Automatic Transmission
By Trista L. Pollard |
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1 When self-propelled vehicles first drove onto the scene, they had manual transmissions. Automatic transmission was eventually introduced in 1939. This type of transmission will switch to the best gear for the speed of the vehicle without intervention or help from the driver. The driver only needs to start the vehicle, operate the accelerator, and use the gear shift for reversing the vehicle. The automatic transmission used on modern American cars usually has a torque converter and a set of planetary gears. The torque converter is a device that transmits the engine's power to the transmission by using hydraulic fluid or fluid that causes motion. In the torque converter there are two parts known as impellers. The impellers may resemble the shape of two fans or they may have different shapes so that they turn are at different rates. As the engine turns one impeller, the transmission fluid that is circulating between them is pushed toward the second impeller. As the fluid flows to the second impeller, it causes the second impeller to twist (exhibit a torque). It is this movement by the second impeller that causes a moving vehicle to continue its movement or to start movement in a stationary vehicle. If the vehicle is stopped or braking, the fluid will continue to flow through the second impeller without having any effect.