Advances in engineering technology in recent years have brought demands for gear teeth, which can operate at ever increasing load capacities and speeds. The gears generally fail when tooth stress exceeds the safe limit. Therefore, it is essential to determine the maximum stress that a gear tooth is subjected to, under a specified loading. When failure occurs, they are expensive not only in terms of the cost of replacement or repair but also the cost associated with the downtime of the system of which they are a part. Reliability is thus a critical economic factor and for designer to produce gears with high reliability they need to be able to accurately predict the stress experienced by the loaded gear teeth. The major problems being faced in the gearbox manufactured by Kay Kay Industrial Corporation, Patiala are interference, surface fatigue and fracture. In order to analyze the exact failure point and the stress levels at which gear is failing, the modeling and stress analysis of the gear box has been done in Pro-E & ANSYS respectively. The necessary design modifications have also been made to rectify these problems.