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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.

The widespread use of finite element models in assessing system dynamics for NVH evaluation has led to a recognition of the need for improved procedures for correlating models to experimental results. With the greater occurrence of finite element models preceding the first prototype hardware, it is now practical to employ pre-test analysis procedures to guide the execution of the tests in the correlation process. This aids in the efficiency of the test process, ensuring that the test article is neither under nor over instrumented. The test-analysis model (TAM) that results from the pre-test simulation provides a means to compare the test and model both during the test and during the model updating process. This paper discusses procedures for pre-test analyses and demonstrates their application to the correlation of a transmission side cover.