The invention of the automatic transmission was one of the most innovative feats of automotive engineering after the invention of the car itself. We’ll break down the workings of an automatic transmission here so that it is more easily understandable.

What does a transmission do?
A transmission transfers power from the engine to the wheels and ensures that both the engine and the wheels spin at an optimum rate. This allows the appropriate acceleration to be generated for the car to move at the desired speed.

Difference between a manual and automatic transmission
A manual transmission uses the clutch and manual shifting of the gears to achieve the appropriate gear for the speed the car needs to go at. An automatic transmission will change the gears itself so all that the driver needs to do is press the gas pedal and brake when needed.

The Torque Converter
This is the component which sits between your engine and your transmission and takes the place of the clutch. It multiplies the torque (spinning power) generated by the engine and also transfers the power generated by the torque to the transmission input shaft. It does this by means of hydraulic pressure from the transmission fluid.

Within the torque converter power is sent from the engine to the pump of the torque converter. The pump transmits this power to the torque converter’s turbine by means of the transmission fluid. The turbine sends the power right back to the pump via the stator. The stator has the important job of multiplying the power of the transmission fluid so that the pump can send more power to the turbine.

Planetary Gear Set
This consists of the Sun Gear, the Planet Gears and their carriers and the Ring Gear. The planetary gear set allows the automatic transmission to generate different gear ratios. Based on which gear set locks and which moves it can create different outputs and inputs and so generate different gear ratios. This allows the vehicle to move at different speeds.

Disc Clutch and Brake Band
This is the system of brakes and clutches which selects which of the planetary gears will be moving and which will be stationary so as to create different inputs and outputs and thus generate different gear ratios.

The different parts of the automatic transmission that connect to each other and control each other’s functioning are all important and extremely complex. The above is a simple, watered down overview of how this complex process is accomplished.