Gear Noise Reduction of an Automatic Transmission Through Finite Element Dynamic Simulation

Numerous authors have previously published on the effects of system dynamics on gear noise in automotive applications [1,2]. It is now widely understood that the torsional compliances and inertias of propeller shafts and pinion gear sets are a controlling factor in final drive gear noise for rear wheel drive vehicles. Considerable progress has been achieved in using finite element simulations of the driveline dynamics to improve the system in regards to gear noise. However very few published results are available showing the application of dynamic simulation methods to automatic transmissions which require considerations of the complications due to epicyclical gear sets.

This paper documents the successful application of finite element dynamics modeling methods to the prediction of gear noise from the gear set in a rear wheel drive automatic transmission. The model was used to investigate the effects of component inertias, stiffnesses, and resonances. Specifically, the ring gear and shaft resonances and the tail stock housing stiffness were found to be significant design factors which influence the gear whine.

Model construction issues will be discussed as well as correlation of predicted gear noise traces with operating measurements. Finally, a comparison will be provided of the noise reduction achieved by incorporating the recommended design modifications into prototype hardware.