A gearbox operating system shifts between 2-wheel and 4-wheel drive. The system includes a reversible motor, and a reduction gear train that is configured to be driven by the motor to move a plunger between extended and retracted plunger positions that shifts gears. A printed circuit board has at least two Hall effect sensing circuits. A magnet is carried by the reduction gear train and is rotationally movable relative to the Hall effect sensing circuits. A first Hall effect sensing circuits provides a first output signal indicative of the extended plunger position. A second Hall effect sensing circuits provides a second output signal that is indicative of the retracted plunger position. A controller monitors the two Hall effect sensing circuits to determine if a desired plunger position has been achieved and trigger an error code if the desired plunger position has not been achieved within a predetermined response time.