In the course of driving

the installing structure of the power train has great influence on the gearbox vibration modes and dynamic fatigue.For the gearbox cracking problems of a light truck

taking its working environment into consideration and combined with the modal theory

the vibration signal acquisition and operational modal analysis are carried out.The relation between gearbox cracking and modal of vibration is discussed.The analysis results offer foundation for the dynamics optimization design of the gearbox structure

which aims at reducing vibration and noise.