Develops a comprehensive analytical procedure for predicting faults in gear transmission systems. A model is developed to simulate the effects of pitting and wear on the vibration signal under operating conditions. The model uses gear mesh stiffness changes to simulate the effects of gear tooth faults. The predicted results were compared with experimental results obtained from a spiral bevel gear fatigue test. The Wigner-Ville Distribution (WVD) method applied to the results were compared to other fault detection techniques to verify the WVD??s ability to detect the pitting damage and determine relative performance.