A transmission is a machine in a power transmission system, which provides controlled application of the power. The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. The function of any transmission is transferring engine power to the driveshaft and rear wheels (or axle half shafts and front wheels in a front-wheel-drive vehicle). Gears inside the transmission change the vehicle's drive-wheel speed and torque in relation to engine speed and torque.
Manual and automatic are the two types of transmission but there are different kinds of automatic transmissions like Automatic Transmission, Continuously Variable Transmission, Semi-automatic transmission and Dual Clutch Transmission.
As the name suggests, an automatic transmission is a fully automatic transmission that can change gear ratios while driving and frees the driver from having to shift gears manually. An automatic transmission consists of three main components: fluid / hydraulic clutch, planetary gear train and hydraulic control.
There are three types of transmissions in use—manual, automatic, and CVT transmissions—each geared toward specific needs and driving styles.
A smooth and light input will result in good efficiency and in most cases comes very close to the efficiency numbers you can achieve from a manual gearbox equipped car. Thus a DCT is the best all-around package, especially if your driving scenario isn't limited to just city or highway driving.
The 1 2 3 gears in an automatic
The first gear is suitable when driving down steep or hilly terrain. The second and third gears are ideal for ascending a hilly terrain or rough roads. These transmission gears allow auto drivers to cruise mountainous terrains, snow, gravels, and other poor traction road conditions.
D and S in an automatic car
D stands for regular Drive mode. This is similar to drive mode in other vehicles. The S stands for Sports mode and will engage a few extra features when driving in that specific mode. Simply move the gearshift to either the D or the S depending on which mode you would like your vehicle to drive in.
The main components of an automatic transmission include the torque converter, planetary gearset, pump, clutches, bands, sensors, valve body, and last but not least is the transmission fluid, otherwise known as ATF.