An overload protection in a drive unit for a steady or jack for a caravan comprises an electro-mechanical control system. A spindle is driven by a motor through a gearbox, wherein the motor is controlled through a power supply. A control device in the system comprises a movable part slidably seated on an output shaft of the gearbox, where the movable part is connected with the spindle. Movement between the shaft and the sliding part is counteracted by springs. The slidable part is provided with actuating points that may contact switches by axial movements. When a nut on the spindle reaches an end position, a reactive force in the spindle will cause the part to move against the force of springs, eventually actuating a switch and thereby causing interruption of the circuit, thereby protecting motor and engagement between nut and spindle from electric and mechanical overload.