A railcar draft gear spring assembly including an axial stack of spring units. Each spring unit is formed from a non-circular elastomeric preform having a series of spaced corners with recessed sides extending between the corners. The preform includes a lobe formed at each corner for channeling the flow of elastomer when the preform is compressed between a pair of non-circular metal plates. Each plate has an outer profile and a series of grippers extending in a common direction away from one surface of the plate. The grippers are arranged in a predetermined pattern relative to each other and relative to the preform for initially positioning the non-circular preformed block of copolyester elastomer relative to the plates and for thereafter restricting the flow of elastomer relative to the outer profile of the plates.