The invention provides a method of replacing the wheels of a railroad car while the railroad car is at rest on rail tracks. Most advantageously, the rail car need not be uncoupled from adjacent cars. The method also has the advantage that rail cars are jacked at the coupler thereby making the method applicable to all types of cars including grain and oil cars which cannot be jacked in their midsections. The method comprises the steps of: releasing the wheel to be replaced from the rail car; transverse insertion of a jack between the rails and the underside of the coupler; actuating the jack to lift the rail car supported upon the underside of the coupler; removing the wheel to be replaced; replacing the wheel; actuating the jack to lower the rail car onto the replaced wheel; securing the replaced wheel to the rail car. The invention also provides a jack for raising and lowering an end of a railroad car having a coupler extending therefrom, the railroad car being at rest on longitudinal rail tracks, the jack being disposed between the rails and the underside of a coupler, the jack comprising: a base supported upon the rails; a cap disposed in parallel above the base; coupler support means for supporting the rail car coupler upon the cap; and lifting means, disposed between the base and cap, for selectively raising and lowering the cap relative to the base between a collapsed position wherein the jack is clear of the rail car to facilitate transverse insertion between the rails and the underside of the coupler, and a maximum lift extended position. Advantageously the coupler support means comprise a travelling table means for shifting the coupler transversely thereby aligning the rail car wheel flanges on the rail head.