Analysis of Drive Line Vibration and Boom Noise in an All Wheel Drive Utility Vehicle 2014-01-1975

The customer demand for all wheel drive (AWD) vehicles is increasing over the period of time which also requires NVH performance on par with front wheel drive vehicles. AWD vehicles are equipped with power transfer unit, propeller shaft and independent rear differential assembly to achieve their functional requirement. The additional drive train components in AWD vehicles may amplify torsional fluctuations in the drive line. Hence achieving the NVH performance of AWD vehicles on par with FWD vehicles without any major change in the existing design is a major challenge. In this work, an AWD vehicle with severe body vibration and booming noise is studied. The operational measurements are taken throughout the drive train on all sub-systems from engine to the rear part of the body in the problematic operating condition. An operational deflection shape analysis is conducted to visualize the vibration behavior of the drive train. The result of analysis shows that the dynamic torsional fluctuations of the drive shaft and rear drive module (RDM) vibration are the major contributors for the high levels of vibration and noise. Powertrain torsional vibration measurements are also carried out with and without the part of the drive train that belongs to AWD. The reduction in vibration to certain extent is achieved by optimizing the stiffness of RDM mounts. The complete vibration and boom is eliminated by installing a tuned mass damper on RDM. The reduction of 4 dB (A) in interior noise and 5 dB in seat vibration are achieved with the effect of modifications.