Today's emerging 4-wheel-drive and all-wheel-drive vehicle architectures have presented new challenges to engineers in achieving low driveline system noise. In the meantime there's also a constant pressure from increasingly stringent noise level requirements. A driveline system's NVH (noise, vibration and harshness) performance is controlled by various noise sources and mechanisms. The common noise issues include the axle gear whine, driveline imbalance/run-out, 2nd order kinematics, engine torque fluctuation, engine idle shake etc. Unfortunately various design alternatives may improve some NVH performance attributes while degrading others. It is important to balance the requirements for these noise sources to achieve an optimized driveline system NVH. However, very little literature is found on this topic. In this paper, discussions on methodologies in balancing these different driveline NVH requirements are presented. Through FEA studies on example driveline systems, the modal mapping strategies of the driveline system are presented. These system level requirements can then roll down to component level technical specifications, such as mounting location arrangement, bushing rates determination, propeller shaft modal placement, joint torsional dynamic compliances, attachment impendence design etc. An example design process for an optimized driveline system is then presented, which is validated in the vehicle testing.
