Commercial Driver’s License (CDL) HW Practice Test

An automatic transmission changes gears through the driver’s gear selector input and the transmission’s internal hydraulic control. You use a lever or push-button to choose the desired gear (Park, Reverse, Neutral, Drive, etc.), and the transmission automatically shifts to the appropriate gear using hydraulic pressure, valve body control, and actuators. The torque converter is a power-transfer component between the engine and transmission and does not perform gear shifts by itself. Range control levers exist on some systems to select a lower or higher range, but they’re not the universal method for changing gears. So the lever or button is the mechanism the driver uses to set the gear, while the transmission handles the actual shifting internally.