This paper deals with the linearized dynamics of a high-speed spur-gear pair supported on linear orthotropic bearings. The mating teeth are modeled accurately and the effect of the dynamic stiffness variation on the dynamic response is taken into account and, in fact, forms the essence of this work. The resulting six degree of freedom system is nondimensionalized in order to reduce the model to a minimum number of independent parameters and to make the results valid for a wide range of practical situations. The equations are solved using a recently developed approximation technique using Chebyshev polynomials. It is shown that not accounting for the periodic variation of the stiffness can lead to drastic differences in dynamic response and stability.