Delmar Roos invented and Willys Overland patented this dual-driving-axle suspension on November 27, 1941.

According to the patent, “‘This invention relates to spring suspension for motor vehicles, and more particularly to vehicles of heavy duty or commercial type wherein the four rear wheels are mounted on tandem driving axles.

One of the principal objects of the invention is to provide means of mounting or connecting the axles to the chassis frame in such a manner so as to permit independentl vertical movement of the axles with respect to the frame without setting up undue strains in the connecting means, or materially restricting the vflexibility of the springs as the vehicle travels upon rough or uneven road surfaces or terrain.”