Multi-physics approach for analysis of transmission rattle

The internal combustion engine produces a fluctuating torque due to combustion as well as induced inertial imbalance in the reciprocating motion of pistons. When the clutch is engaged, the resulting torsional oscillations of the crankshaft are transmitted to the transmission. In the transmission the fixed driving gears (pinions) transfer the motion to the driven unselected gears (loose gears) through impacting teeth pairs in close proximity due to the compact nature of modern transmission systems. The driven gears in turn rotate freely on their bearings, as they are unselected (referred to as loose gears). As a result, the idle (loose) gears oscillate within their backlash limits, leading to impacts with the driving gears. The vibrations caused by these impacts are transferred through the transmission shafts and their support bearings to the transmission bell housing, and is mostly radiated as sound that resembles the noise produced when a marble rolls inside a metallic can. This sound is onomatopoeically referred to as rattle.