Glossary of Automotive Terms - Automatic Transmission
What Automatic Transmission Means:
An automatic transmission, also called auto, self-shifting transmission, or AT, is a type of motor vehicle transmission that automatically changes the gear ratio as the vehicle moves, meaning that the driver does not have to shift the gears manually. Like other transmission systems on vehicles, it allows an internal combustion engine, best suited to run at a relatively high rotational speed, to provide a range of speed and torque outputs necessary for vehicular travel. The number of forwarding gear ratios is often expressed for manual transmissions as well (e.g., 6-speed manual). The Automatic transmissions have hydraulically operated gear sets, which require no gear shifting or clutching by the driver.