In this research dynamic analysis of a one-stage gearbox system was carried out utilizing bondgraph approach. The system under investigation is 8 degrees of freedom gearbox unit. In this system a crack was imposed to one of the spur gears with varying crack size. The proposed method is used to derive the governing equations of motions, which was appropriate for gear fault detection purpose. The status of the tooth deterioration can be evaluated mainly by introducing the reduction in the ...