A rotational power transmission apparatus is provided including an input coupler having first and second input shafts, a differential engine coupled to the first input shaft and transmitting power to a first output shaft. First and second one-way bearings are coupled to the first output shaft. A first torque converter is coupled to the first one-way bearing, and a second torque converter coupled to the second one-way bearing. An output coupler is coupled to output from the first torque converter, output from the second torque converter and a second output shaft.