Rattle noise and high levels of vibration in agricultural tractors lower the productivity of the operators and may cause serious health issues in them. This study examined a method for preventing resonance and reducing the torsional vibration that causes rattling in tractor power take-off (PTO) drivelines in the idle state using a two-stage torsional damper. The PTO driveline was simplified to a 6-DOF model based on the principle of equivalent mass moment of inertia using commercial simulation software. The variations in the angular velocity of the PTO drive shaft in an actual tractor were measured and compared to the simulation results using a single-stage torsional damper to validate the model. Using this validated PTO driveline model, the pre spring of a two-stage torsional damper was investigated to determine its optimal torsional stiffness to minimize torsional vibration. The simulation results showed that the variations in the angular velocity of the PTO drive shaft decreased as the torsional stiffness of the pre spring decreased; accordingly, an appropriate torsional stiffness reduced the variation in the angular velocity delivered to the PTO drive shaft. The optimal torsional stiffness of the pre spring was determined by considering the manufacturing limitations of the torsional damper and the magnitude of the input engine torque. A pre spring with this optimal torsional stiffness was installed on an actual PTO driveline to measure the angular velocity transmissibility, which was the ratio of the variation in the angular velocity of the engine flywheel to the variation in the angular velocity of the PTO drive shaft, and the results were compared with those of the simulation. When the angular velocity of the engine was 850 rpm, the angular velocity transmissibility of the PTO drive shaft was 0.4 in the actual test, similar to the value of 0.29 obtained using the simulation. Thus, the simulation-optimized pre spring was able to avoid the resonance domain, while considerably reducing the torsional vibration that leads to rattling. The results of this study support the safe operation of agricultural tractors and guide the evaluation of torsional damper configurations of different vehicles.