What does the hydraulic system control in an automatic transmission?

The hydraulic system in an automatic transmission is responsible for the engagement and disengagement of gears. This is achieved through the use of hydraulic fluid, which is pressurized and directed to various components within the transmission. When the driver accelerates or decelerates, the hydraulic system responds by altering the pressure to activate clutches and bands that engage or disengage the gears, allowing for smooth shifting without the need for manual intervention.

This hydraulic control system is crucial as it enables the transmission to change gears automatically based on the vehicle's speed and load, optimizing performance and fuel efficiency. The ability to manage these transitions seamlessly is one of the defining features of an automatic transmission, distinguishing it from manual systems where gear changes are made by the driver.