Based on the centralized parameter method

an 8 degrees of freedom dynamic model and dynamic equations of spiral beveled bevel gears were established. Considering the static transmission error

tooth surface friction and tooth clearance comprehensively

the dynamic responses of transmission system were solved by Runge-Kutta algorithm with variable step lengths

and the effects of friction coefficient and coincidence degree on the vibration amplitude of the transmission system were studied. The results showed that the friction coefficient was different under different working conditions. With the decrease of lubricating oil

the friction coefficient

the system’s vibration displacement and normal meshing force increased; coincidence degree was reduced

but vibration amplitude and normal meshing force increased while the angle between the contact trace and the root cone increased.