AbstractIn this paper, a method to determine elastohydrodynamic film thickness in helical gears is developed by combining the Dowson‐Higginson elastohydrodynamic lubrication (EHL) formulation with helical gear geometry and kinematics. Comparisons are made with traditional gear film thickness models. This analysis is then used to characterise the film thickness and lambda ratio in an automotive planetary gearset. Methods to measure surface roughness in fine‐pitch gears are described.