Aiming at drive bridge gear whine occurring in gear coast stage for one light passenger vehicle,a method of tooth topology modification was proposed to optimize the whine noise of drive bridge main reducer gear.The road test experiment was done by using LMS Test.Lab device.The noise source was found from meshing vibration of main reducer gear of drive axle.The current tooth contact performance of main reducer gear was analyzed.On this basis,the tooth surface topology modification method was proposed to correct the current tooth contact area and transmission error.Contrasting the load meshing performances and NVH simulation curves between the current tooth surface and the modified tooth surface,the simulation results indicate that the tooth meshing performance and NVH performance after modification are all improved.Finally,the road test experiments were executed for the current tooth surface and the modified tooth surface of main reducer gear.The experiment results indicate that the gear whine is improved obviously after modification.