Due to improving levels of vehicle refinement and the growing importance of vehicle sound quality, transmission whine is an issue of increasing interest to vehicle manufacturers. This paper describes the development of a set of novel tools for the prediction of gear whine from spur and helical external gear systems.Transmission whine is primarily generated by transmission error, which is a deviation of meshing gears from a perfectly conjugate (smooth) motion due to manufacturing tolerances, tooth corrections and elastic deflection due to transmitted torque. The transmission error excites the geared shaft and bearing system leading to dynamic forces at the bearings, which in turn excite the transmission casing causing it to radiate noise.The first stage in the simulation of gear whine is the analysis of tooth contact conditions based on the gear macro geometry (module, facewidth, addendum corrections, etc.) and micro geometry (profile and lead corrections) in order to calculate transmission error and mesh stiffness variations. The transmission error and mesh stiffness data are then used by newly developed software to excite a dynamic model of the geared shaft and bearing system and thus calculate the dynamic loading on the bearings. This new software calculates the system behaviour in the time domain in order to allow feedback of gear misalignment and centre displacement due to shaft deflections into the calculation of the excitation force. The significance of including these dynamic loading effects is demonstrated in this paper.The calculated bearing loads are used to force a finite element or boundary element model of the transmission in order to predict the casing vibration and radiated noise. Noise and vibration measurements have been made of a modelled transmission to validate the results of the simulation.