Abstract: An all purpose wagon vehicle for general farm use, including an undercarriage frame on which is provided a dump box having a floor and fixed front and side walls standing thereover, with the dump box being tiltable on the undercarriage frame to discharge whatever it carries rearwardly, and a rear wall closure door which is hinged to the side walls forwardly of the normal upper back edge corners to open only upon the appreciable tilting of the dump box and without ground interference. And, a special latching mechanism operative in the course of tilting the dump box on the frame, to automatically allow the closure door to open or be held closed.