Transmission Kickdown Solenoid Operation:

Like all solenoids, it receives a voltage signal that excites an electromagnetic coil that pushes or pulls a plunger/linkage to function as a movement actuated controller. Transmission kickdown solenoids are used for downshifting to the next available lower gear to gain speed and torque quickly. They're also vibration resistant, rated for high temperature environments and can operate even when immersed in fluids.