High Frequency Gear Whine Control by Driveshaft Design Optimization 2003-01-1478

Generation mechanism of transmission gear whine varies significantly by gear position, frequency and path/amplifier of the total system. Although controlling the source, namely transmission error/dynamic meshing force of the gears is desirable; it is not always feasible as well as most effective. This paper describes the root cause analyses of high frequency gear whine (overdrive position) of commercial vehicle, which combined in-depth experimental and CAE analyses. The generation mechanism of the gear whine is clarified efficiently utilizing Ford Spin-Torsional AWD NVH Test Facility, state-of-the-art Powertrain NVH development test cell, combining vehicle and sub-system NVH measurement. The analyses results showed the O/D gear whine is driveshaft airborne, due to alignment of driveshaft higher bending resonance to air-borne mode (“breathing mode”). Integrating experimental verification with changing the modal characteristics (de-coupling) by changing mass property of the driveshaft, and utilizing CAE modeling optimization with newly developed acoustic simulation technique to estimate radiation noise of the driveshaft, the most efficient countermeasure was developed. Final countermeasure effect to gear whines was verified with production vehicles to confirm significant effect to satisfy the customer requirement.