Abstract: An improved apparatus for automatically extending and retracting the landing gear of a semi-trailer. The apparatus includes a reversible electric motor and speed reducer removably drivingly securable to an existing manually operated mechanism for extending and retracting a landing gear. Electric circuitry is provided for permitting an operator to control the extension and retraction of the landing gear from within the cab of a tractor and, alternately, from the exterior of the semi-trailer. The electrical circuitry provides both audible and visual indication of the position status of the landing gear and automatic cutoff of the electric motor when the landing gear is fully extended, and alternately, when the landing gear is fully retracted.