Effect of dry friction damping ring(DFDR) on vibration characteristics of high speed large power density gear transmission(HSLPDGT) is studied. A coupling multi-body dynamic model of gear transmission with DFDR is built. In the model, the damping effect of DFDR on transmission, the varying meshing stiffness and transmission error are considered. A DFDR test system of gear transmission is developed. This DFDR test system has the highest input speed of 36 000 r/min and oil lubrication. This model is verified ...