The objectives of this study were to analyze gear rattle in a power drive line using its dynamic model and to derive design guidelines to eliminate it. A 72 degrees of freedom model of power driveline of an agricultural tractor was developed and proved to be valid fer predicting the collision characteristics of gears in mesh, which may determine whether or not the gear rattle will occur. Using the model the effects on the rattle of drag torque, backlash, mass moment of inertia, transmitting torque were analyzed. Increasing drag torque or decreasing mass moment of inertia reduced gear rattle. The gears transmitting power do not develop rattles. It was also found that a large amount of rattle is likely to be developed by the change gears placed at the end of idle shafts. Increasing the drag torque to such change gears may be the most effective way of reducing the gear rattle in a tractor driveline.