Abstract: A hydraulic stabilizing device utilized to dampen the sway of railway cars comprising a double acting hydraulic cylinder having a center position wherein the fluid is locked in the opposing chambers of the cylinder except for high pressure relief once the piston is forced out of the center position as the railway car traverses a curve. Longitudinal groove means in the cylinder barrel opens up a restricted bypass across the cylinder piston so as to allow a conventional dampening function at all other positions of the cylinder except the center position. The stabilizer cylinder also includes a concentrically spaced sleeve surrounding the cylinder forming a precharged accumulator chamber for resupplying either of the cylinder chambers through check valves in the cylinder heads.