Quasiclassical trajectory calculations have been performed to study intramolecular vibrational energy redistribution (IVR) from CH overtone states in benzene. The rate and extent of this redistribution is sensitive to details of the potential energy surface. A particularly important potential energy surface property is attenuation of the HCC bending frequency upon CH stretch excitation. This property gives rise to non-irreversible IVR when the CH stretch is highly excited. An analog to quantum beats is observed in phase averaged quasiclassical trajectories.