The present invention provides a retrofit system for configuring a vehicle into a hybrid electric vehicle or electric vehicle. The system comprises an electric power source (EPS) comprising one or more motors to provide fail safe torque to the vehicle and harness braking energy for charging one or more batteries, one or more attachable electric power gear assemblies (EPGA) configured to couple the one or more motors to a propeller shaft for providing the torque to the vehicle, and an electronic control unit coupled to the electric power source (EPS) for dynamically controlling functioning of the one or more motors based on the running conditions to drive the vehicle. The system comprises of a motor controller to control functioning of one or more motors. The motor controller actuates one or more motors based on the torque and power required to drive the vehicle.