A rotorcraft drive system is a complex and tightly coupled system that performs the function of transferring engine power with speed reductions to the lifting rotor, anti torque device and other accessory systems while minimizing transmission power losses. The preliminary design of this system takes into consideration the vehicle concept, power requirements, airframe layout for engine and transmission housing, and gear optimization. The optimization evaluates parameters and design options such as gear type, diametral pitch, material, helical angle, shafting and overall configuration. The paper discusses a modern systems engineering and Product Lifecycle Management (PLM) approach focused on improved redesign capability and design integration. A digitized modeling and simulation environment was created to perform optimization with gear structural analysis and parametric Computer Aided Design (CAD). Also discussed is the implementation of this methodology for a multi-role helicopter drive system design.