The transmission of traction electric motor torque to the electric locomotive wheelset is carried out through a wheelset reducer with cylindrical gears with straight or inclined teeth. The wheelset reducer is one of the most important units of a modern electric locomotive. It bears significant alternating loads when the locomotive starts, accelerates and stops. It is of paramount importance to choose the right drive option, which the locomotive movement and dynamics of its running depend on. At high running speed, the system must be reliable in terms of the oscillations of locomotive unstrung masses. The thirty-year operation of electric locomotives in Bulgaria has shown a number of shortcomings of wheel reducers that cause difficulties with operation and repair activities in locomotive depots. The paper presents a strength analysis of a transmission mechanism, that has shown low operational reliability leading to locomotive derailment. The results of analysis have indicated the areas, which need monitoring in operation to prevent the occurrence of incidents and accidents due to the transmission mechanism operation.