The development of new products and services allows railway transport to constantly increase the fleet of specialised wagons, which, in comparison with the universal rolling stock, have the best technical and economic indicators. A significant part of cars is delivered by railways, and it is economically reasonable to transport them on a specialised rolling stock. In this regard, the development of a methodology for refined theoretical studies of the strength of bodies of a double-deck rolling stock for passenger cars transportation, the choice of appropriate design schemes and parameters of the bodies, the analysis of the frequencies and forms of their natural oscillations, taking into account the finite stiffness of the elements, are urgent research tasks. The research uses the methods of structural mechanics of rod systems, the applied theory of elasticity, and discrete masses. A wide range of frequencies and forms of the natural free oscillations was obtained using the discrete mass method for a structural scheme with load transfer from the upper to the lower level of the wagon with the help of four racks. The applied methodology of theoretical determination of frequencies and forms of the natural free oscillations of the car transporter wagon by the method of discrete masses is effective. It allows for the estimation of the dynamic characteristics of the wagon.