Browse Publications Technical Papers 1999-01-1765
1999-05-17

Methodology: Automatic Transaxle Lash Study for Park Disengagement Clunk 1999-01-1765

The purpose of this paper is to explain a methodology for diagnosing noise and vibration of internal components of the automatic transaxle and particularly for park disengagement clunk.
The method for determining contributing lash is three-fold. First the lash values are physically measured. Secondly, in-vehicle test data is taken using accelerometers, microphones, and stress gages. The data is taken at a baseline condition and then when various lash interfaces are set at zero. Thirdly, component impact testing can be done to identify noise contributing parts.
For the condition of park disengagement clunk this method helps to diagnose the source of the noise. When a vehicle is parked on an incline and the transaxle put in park, there is an energy transfer of the weight of the vehicle through the transmission and onto the suspension of the vehicle. When the transmission is pulled out of park, the released energy results in a loud clunk. The clunk has a high and low frequency content. This study shows how the higher frequency responses of the transaxle internals can be identified.
The suggestion that this method makes of grouping components together to find particular NVH contributors is significant for reducing costs and test time. The result is an opportunity for reducing the specific lash(es) that contribute to automatic transaxle noise and vibration. The methodology is demonstrated on the park disengagement clunk problem and can also be used for other transaxle NVH phenomena such as tip-in and back out clunk. It can be used to diagnose noise and vibration for rear wheel drive transmission applications as well.

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