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Powertrain torsional vibration has become a subject of increasing concern for the heavy duty truck industry in recent years. This is due in part to truck and diesel engine developments, and to drivetrain system trends. A computer simulation is an effective tool in analyzing this problem. A powertrain vibration analysis program has been developed by the authors. It has been used extensively in the evaluation and optimization of powertrain system performance. In this paper, first the heavy duty powertrain is characterized as a vibrating system. Its natural frequencies, mode shapes and frequency response characteristics are reviewed. Second, the theory of torsional vibration and its application in the simulation are described. The drivetrain is described as a discreet model. An undamped modal analysis is given as an eigenvalue problem.

Quality control of NVH performance of Body and Chassis systems is a challenging task. In-line NVH monitoring is part of a practical solution in many cases. The associated technology is maturing, flexible, and economical. Benefits extend beyond a “safety net” sorting function. This paper presents a general overview of the current state of commercially available technology, and presents an example application of an in-line NVH monitoring system for a window regulator assembly line. A couple specific issues and resulting NVH monitoring techniques are discussed - the use of an enveloping function to highlight a cable interference issue, and the use of a microphone to highlight a motor noise issue in a relatively noisy environment.