The following thesis document researches into creating a model to represent the behavior of a wind turbine gearbox. This model is developed based on the overall parameters of a NORDEX N90 2.5MW wind turbine developed by a German company Nordex SE. This research focuses on the combination of a flexible body and a multibody dynamics analysis software. This is done through the usage of MSC ADAMS, a multibody dynamic analysis program, and MSC Patran/Nastran, a finite element analysis software, and its associated solver. The model is created to show the vibration patterns of a healthy gearbox with rigid bodies, with a flexible body, and with a defect applied on a particular gear in the planetary gear systems that is representative of the N90 wind turbine. The flexible body incorporation allows for stress analysis of different gear teeth at different locations. Using this model a vibration signature is generated for a specific type of defect.