<div class="htmlview paragraph">Noise generated by vehicles has become of increasing concern, in recent years, in its effect both inside and outside the vehicle. Although the noise contributed by heavy-duty automatic transmissions in on- and off-highway vehicles is insignificant in relation to that generated by other vehicle components, a program was initiated to investigate sources and causes of transmission noise and to</div> <div class="htmlview paragraph">develop methods of reducing or eliminating that noise.</div> <div class="htmlview paragraph">In power transmission, the most common source of noise is vibration of individual gears in mesh. Two methods of decreasing gear mesh vibration have been found successful: improving gear tooth profile and counterphasing planetary gearing.</div>