Abstract: The disclosed jack assembly has an elongated structural beam of sufficient length to extend between and beyond the two rails of a railroad track to be supported on top of the rails. A compact power lift cylinder, in the form of a multiple-sleeve power cylinder, is connected to the beam; and a car engaging plate is coupled to the power lift cylinder, to be moved in a direction transverse to the beam. The silhouette of the beam, power lift cylinder and plate is low, when the power lift cylinder is contracted, to allow them to be fitted with clearance to a lifting position, under a railroad car with the beam extended across the track rails and the car engaging plate vertically aligned under the railroad car frame. The power lift cylinder has a power stroke sufficient to lift the overlying railroad car enough above the rails to remove the railroad car completely from one wheeled truck assembly, for replacement or the like.