A powertrain system for a vehicle includes an electric power source having a first motor configured to provide a first amount of torque to the vehicle and a second motor configured to provide a second amount of torque to the vehicle different from the first amount of torque. The system further includes one or more attachable electric power gear assemblies configured to couple the two or more motors to a propeller shaft for providing the torque to the vehicle. The system includes an electronic control unit coupled to the electric power source and configured to dynamically activate or deactivate each of the first or second motors based on one or more operating conditions of the vehicle. The first and second motors comprises at least one of a same number of poles or a same number of phases.