A method,which compares the angular acceleration and vibration spectrums of shafts and gears with physical characteristics of gearbox as tooth numbers and speed ratios,is proposed to find the source of gear rattle vibration.A mathematical and multi-body dynamics co-simulation model is built to reproduce the gear rattle phenomenon of one typical type of manual transmission.In the model,multi-body dynamics part is used for rotational motion and engagement simulation of gearbox shafts and gears,while mathematical part for control and data processing.The simulation results show that the sound source of the gear rattle from the first gear to the third gear is similar to the experimental results;different parameters like rotating damping,contact stiffness,contact damping,inertia moment and torque fluctuation making effects on gear rattle vibration strength are researched and simulated.The comparison of the simulation and experimental results shows that this method can provide recommendations for solving practical gear rattle problems.