The paper clearly shows some tests of cogged wheels and gears of traction gearboxes of locomotive wheel-motor units and multiple rolling stock for compliance with state standards. The test procedure and control methods for compliance with mechanical properties, hardness, surface quality, micro- and macrostructure are described. The features of magnetic powder technology and capillary non-destructive testing methods for detecting cracks in cogged wheels and bearings are considered. The measuring tools and test equipment, including auxiliary materials used in flaw detection, are given.