A transmission can be manual, automatic, or continuously variable. Transmissions adjust the power to the wheels for different applications. Maintaining a steady speed requires less power than accelerating to that speed.
Manual Transmission. In manual transmissions the driver must use a clutch before shifting gears by hand with a gear stick shifter. Manual transmissions commonly come in 3, 4, 5, or 6 speeds.
Automatic Transmission. An automatic transmission uses a torque converter with transmission fluid to couple with an engine, providing automatic gear shifting. The operator only has to select a forward or reverse gear. Today there are computer controlled electronic transmissions that calculate the most efficient time to shift.
Continuously Variable Transmission (CVT). CVTs have begun to appear more on passenger cars as the advantages of their use have become more apparent. Instead of using gears, CVTs commonly use two variable speed cone-shaped pulleys in conjunction with a belt for an infinitely variable gear ratio.