A speed sensor system for locomotive traction motors comprising: a mounting bracket affixable adjacent to a traction motor to be monitored, including a sensor support having a hollow tubular portion that extends along a support axis with an internal configuration for releasably receiving a speed sensor; and a sensor assembly comprising: (i) a tubular sensor shell; (ii) a speed sensor element contained in the tubular sensor shell adjacent to one end, (iii) the sensor shell including an exterior surface configured complimentary to the interior configuration of the hollow tubular portion wherein, when seated within the tubular portion, the sensor will be properly positioned and aligned within the mounting bracket relative to a traction motor, the sensor shell having a flattened mating surface on the exterior surface thereof, and (iv) an electrical cable having leads connected to the sensor element attached to the sensor shell, characterized in that: the mounting bracket includes a pin extending generally perpendicular to the support axis and across the hollow tubular portion of the mounting bracket and arranged to be mateable with the flattened mating surface of the sensor shell during insertion of the sensor shell into the hollow tubular portion for properly aligning the sensor in the sensor shell relative to a traction motor. a mounting bracket affixable adjacent to a traction motor to be monitored, including a sensor support having a hollow tubular portion that extends along a support axis with an internal configuration for releasably receiving a speed sensor; and a sensor assembly comprising: (i) a tubular sensor shell; (ii) a speed sensor element contained in the tubular sensor shell adjacent to one end, (iii) the sensor shell including an exterior surface configured complimentary to the interior configuration of the hollow tubular portion wherein, when seated within the tubular portion, the sensor will be properly positioned and aligned within the mounting bracket relative to a traction motor, the sensor shell having a flattened mating surface on the exterior surface thereof, and (iv) an electrical cable having leads connected to the sensor element attached to the sensor shell, (i) a tubular sensor shell; (ii) a speed sensor element contained in the tubular sensor shell adjacent to one end, (iii) the sensor shell including an exterior surface configured complimentary to the interior configuration of the hollow tubular portion wherein, when seated within the tubular portion, the sensor will be properly positioned and aligned within the mounting bracket relative to a traction motor, the sensor shell having a flattened mating surface on the exterior surface thereof, and (iv) an electrical cable having leads connected to the sensor element attached to the sensor shell, characterized in that: the mounting bracket includes a pin extending generally perpendicular to the support axis and across the hollow tubular portion of the mounting bracket and arranged to be mateable with the flattened mating surface of the sensor shell during insertion of the sensor shell into the hollow tubular portion for properly aligning the sensor in the sensor shell relative to a traction motor. the mounting bracket includes a pin extending generally perpendicular to the support axis and across the hollow tubular portion of the mounting bracket and arranged to be mateable with the flattened mating surface of the sensor shell during insertion of the sensor shell into the hollow tubular portion for properly aligning the sensor in the sensor shell relative to a traction motor.