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In order to effectively evaluate automatic transmission gear noise and vibration performance using a hemi-anechoic test facility, it is essential to understand the coupling mechanism between the transmission internals and the dynamometers and associated shafting. Once this coupling mechanism is well understood, each major frequency response of the resulting torsional vibration operating data can be properly categorized according to the source: transmission-internal, facility, or driveshaft. This knowledge helps noise and vibration engineers properly manage vibration peaks in transmission operating data by ensuring that the issue of concern is not inadvertently influenced by the facility system. Analytical simulations and tests were performed on a transmission operated in a hemi-anechoic facility to evaluate gear vibration using various driveshafts, followed by a program of vehicle testing.

The Ford Spin Torsional NVH TEST Facility developed and completed in 1999 as a state-of-the-art powertrain NVH development facility(1). Since then, various designed capabilities have been verified with test vehicles for multiple applications to facilitate powertrain NVH development. This paper describes fundamental capabilities of the test facility, including input module to simulate engine torque signatures of arbitrary engines (“virtual engine” capability) and absorbing dynamometer systems, functioning as a precision 4WD/AWD chassis dynamometer. The correlation between road test/chassis dynamometer test and Spin-Torsional test is then illustrated, verifying high correlation of vehicle/sub-system responses between conventional vehicle testing and Spin-Torsional test results.

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”).

An All Wheel Drive Spin-Torsional Dynamometer facility has been constructed at the Advanced Engineering Center of Ford Motor Company, adding unique capability for powertrain NVH testing. This state-of-the-art facility is designed to concurrently deliver controlled rotational and torsional engine inputs to the drivetrain. While the facility supports the use of a live engine for input, it is also equipped with an engine simulator to allow detailed examination of the NVH characteristics of new powertrain configurations before prototype powerplants are available, without the need for a live engine. This will reduce development timing for new powertrains significantly. The virtual engine consists of a driving dynamometer coupled with a high frequency servo-hydraulic torsional actuator.