Automatic transmission

What its purpose? To provide speed n torque multiplication but the driver dont have and can't select a desired torque/ speed ratio like manual
What's in there? 8 major parts: Input shaft; output shaft; bands n multiplates clutches; planetary gear sets; oil pump; valve body; Servo n piston; torque converter.
While planetary gear set provides different gear/torque ratio; bands n clutches provide clamping 4 gear change, also absord torsion due to sudden torque n locks up.
The oil pump supplies oil to the valve body, lubing all component while the valve body is the automated hydraulic control center for changing gears n different speed/load conditions.
Torque converter replaces the clutch n the flywheel, the central magic of automatic transmission. it has mainly an Impeller, stator n overrunnning clutch, and a turbine, the turbine is the output, fluid is stuck between there. In operation of the torque converter, the main pricipal of moving fluid is cnetrifugal force. The impeller is connected to the engine crankshaft, when engine turns, impeller turns, creating rotational motion, then converts to kinetic motion towards the turbine. The flow hits the turbine vanes got converted into rotational again and kinetically got flown back to the stator, back to the impeller. So it is the centrifugal force that turns the turbine n the stator.

One more notable part is the governor located on the output shaft jut out side the transmission housing, When the output shaft turns faster, centrifugal force open a plunger letting more fluid inside to help increase high oil pressure @ high engine speed.