The uniqueness of heavy and medium duty vehicle powertrain design, compared to that of passenger cars, is two fold: vast variations exist from vehicle to vehicle because of mission requirements, and powertrain components are sourced from a diverse group of suppliers. Vehicle powertrain design involves selection of the appropriate major components, such as the engine, clutch, transmission, driveline, and axle. At this design stage the main focus is on power matching, to ensure that the vehicle's performance meets specifications of gradability, maximum speed, acceleration, fuel economy, and emissions[1, 2, 3, 4 and 5]. The general practice also demands that the durability of the drivetrain components for the intended vocation or application be verified. Equally important but often neglected in the design phase is the system's NVH (Noise Vibration and Harshness) performance, such as torsional vibration, U-joint excitation, and gear rattle. As indicated in this paper, due to higher performance and quality standards, all three types of analysis must be carried out thoroughly in the design. To be effective in dealing with this challenge, potent computer simulation tools with an integrated product database, and a dedicated engineering supporting team are needed. It is universally acknowledged that significant cost reduction is achieved when analysis is done up front in the product development cycle. To support this point, Meritor Automotive's progress as a full system supplier in the use of six of its powertrain system performance prediction computer models is introduced. Direction for future efforts in line with the virtual prototyping concept is explored. Evidence sustains that an integrated drivetrain system approach is beneficial from engineering cost and performance perspectives.