It is shown that the responsible parts of each vehicle are tubular connecting lines, which are included into the braking, fuel and exhaust systems of cars. These pipelines have high requirements for reliability, vibration resistance, strength, corrosion resistance and durability. These parts are used as expanders and connecting elements when transitioning from a smaller pipeline diameter to a larger one. The paper presents studies of the operation of distributing the end of the pipe blank with a rigid punch. In the process of distribution, the acting tangential stresses lead to a decrease in the thickness of the edge section of the workpiece. This entails a decrease in the reliability of this area during operation and a decrease in its maintainability and corrosion resistance. Also, to ensure the tightness of pipe connections, threads are cut or these areas are welded together in the specified areas of the workpieces. Therefore, an important design feature of tubular diffusers is the same wall thickness throughout the cross-section of the semi-finished product. To solve the problem of increasing the thickness of the semi-finished product after distribution, an asymmetric tool is proposed. The task was solved in the finite-element formulation using a special complex of 3D modeling Simulia Abaqus – student edition. The pipe blank was represented as a deformable solid, while the punch was modeled as a completely rigid discrete solid. The construction method for both models is "revolution". According to finite element modeling, dispensing with a conical asymmetric tool has advantages from the point of view of increasing the thickness of the end zone of the pipe bell. The thickness of the part increases by 22.5% from a thickness of 1.77 mm for the classic version of distribution, to 1.82 mm – for distribution with an asymmetric tool. To reduce the thinning of the wall after distributing the pipe blank, it is recommended to use an asymmetric punch. To obtain a symmetrical pipe socket, it is necessary to make two dispensing transitions with a 180° rotation of the blank or punch