A new progressive wear method is used to define the wear for cylindrical gears: This method is based on the contact analysis and uses an iterative process to simulate the actual wear. The result is displayed either in 2-D or in 3-D, to provide a clear evaluation of the various modifications involved, for example, the effect of tip relief on the wear behavior (module ZA31). The wear calculation also includes calculation of the wear factor with nitrided, unhardened, and hardened steels according to Plewe. The calculation also includes the effect of some lubricants, as defined in the measurements taken by the company Klüber.