A railcar shock absorber has neutral position in which the piston is spaced between buff and draft ends of the cylinder. An external spring is mounted to the shock absorber. A slider rod has one end mounted to the coupling to move relative to the frame of the railcar. The spring has retainers on each end, and the slider rod passes through the retainers. One of the retainers is stationary relative to the frame. The other retainer floats relative to the frame and will abut a neutral stop of the frame when the spring is in the maximum length position. An engagement member on the slider rod will further compress the spring if a draft shock occurs from the neutral position. If a buff shock occurs from the neutral position, the engagement member moves away from the floating retainer.