Wind turbines have been used for decades in order to produce electricity. Its main advantage is that its energy is clean, does not harm the nature and maintains its balance. For this reason, researchers and engineers have been focused on improving its design, performance and reliability. In addition, its condition monitoring has been studied for many years by processing its vibration signature. The latter is performed either by collecting it from the real mechanical system using sensors or by modeling its vibration signature. In this paper, a wind turbine drivetrain dynamic behavior is developed under different excitation conditions considering the influence of two-disk brake position. Main key factors involved in the dynamic behavior, such as wind turbine dimensions, gear mesh stiffness fluctuation, driving torque, braking torque and bearing stiffness, are taken into account in the model. To investigate a complex damage case, a typical gear fault, profile error and assembly defect are introduced. The dynamic response of the wind turbine, for healthy and damaged cases, is studied based on time series and spectra of acceleration signals. To diagnose gear faults, three indicators (RMS, STD and kurtosis) are used. Based on signal observations, it can be concluded that the disk brake location, wind turbine characteristics and gearbox defects have a direct influence on the dynamic behavior of the system.