Cam-Driven Member Assembly–Improvements in Clutch Neutral Rattle Performance

Neutral rattle is a characteristic manual transmission gear rattle sound which is caused by the gears oscillating through the backlash inherent to the transmission. This oscillation is caused by engine firing impulses and the sensitivity to these impulses increases as transmission operating temperatures increase and when engine torque loads increase.

Engine torque loads can be directly attributable to the rpm and the driven accessories on the engine (i.e., air conditioner, alternator, etc.). Neutral rattle can be eliminated by increasing the engine idle speed and/or by increasing the dynamic drag torque of the transmission. Each of these solutions, however, reduces the EPA mileage rating and, with the transmission, decreases cold weather shiftability performance. This paper will discuss previously used methods of removing neutral rattle and their design limitations. In addition, a presentation of the “cam” driven member assembly's ability to remove neutral rattle without hindering overall clutch performance will be covered.