This thermal rating method balances the sum of the load-independent iosses and the load-dependent losses against the heat dissipation capability of the gear case. Empirical f??ctors are determined which calirate the calculations against the test muits for assembled gear reducers. The resuits of this calculation method are compared to the testresults from 251 gear reducer tests. in addition@ since loses are caiculatd@ this method can be used to caidate the efficiency of the gear drive for the operating conditions.