The frictional contact behaviour of spline couplings is a complex topic due to the multiaxial, three-dimensional nature of the shaft and tooth loadings, which typically include torque, axial loads and bending moments, as well as local tooth interaction, such as tooth sliding and bending. Three-dimensional finite element modelling is the most readily available solution. However, this is time-consuming, with respect to both model development and run-times, for spline designers, who require the ability to explore the parametric design space rapidly. This paper presents parametric two-dimensional and three-dimensional analyses of spline couplings of the aeroengine type to investigate the effects of changes in spline geometry on key fretting-related and fatigue variables, such as contact pressure, slip and sub-surface stresses. Two-dimensional finite element models were used to assess the effects of the number of teeth, tooth thickness, shaft diameter and coefficient of friction. The three-dimensional spline analyses were employed to verify the trends predicted by the two-dimensional models.