A transient numerical heat transfer model has been developed for the purpose of estimating the time-dependent temperature distribution in a heavy duty drum brake system. The model is based on a forward-difference explicit finite difference solution of the heat equation, in combination with a non-uniform pressure distribution for energy input, based on observed brake lining wear. Temperatures predicted by the model were compared to experimental dynamometer drum temperature measurements. The model was utilized to simulate a common industrial test for evaluation of brake drum resistance to thermo-mechanical fatigue cracking. Thermo-physical property variation and drum wall thickness were shown to exert a strong influence on the predicted temperature gradients and fatigue cracking susceptibility.