The article deals with the problem of experimental determination of the mechanical reliability indicators of motor-gear unit of motor coaches of suburban electric trains. The range of natural frequencies of the casing is compared with the frequencies of disturbing influences. The problem of the influence of torsional vibrations of the traction motor frame as a source of additional dynamic loading of the gear casing is indicated. The value of the rigidity of fastening the casing to the traction motor depends significantly on the method of fastening. If the technology of joining the traction motor and the gearbox is not observed, the range of natural frequencies of the oscillatory system of the casing may change, while the occurrence of resonance phenomena is also possible. The paper presents the amplitude-frequency characteristic of torsional vibrations of the traction motor frame and considers the dynamic moments that occur on the gear casing during torsional vibrations of the traction motor. To reduce the level of dynamic loads on the gear housing, which contribute to the occurrence of failures, the design of the housing with shock-absorbing fastening to the frame of the motor bogie, which provides increased vibration protection of the system, is considered. Determination of critical points of stress in the structure of the gearbox was carried out using the finite element method (FEM).