ABSTRACT−To analyze and model the dynamic efficiency of vehicle transmission system, the theoretical power losses
formulas of the spur/helical gear under the condition of elastohydrodynamic lubrication (EHL) were deduced. The spur gear
meshing efficiency model was validated by comparing the predicted models with measured data. The formulas of oil churning,
windage, and bearing power losses, which are widely applied and fit the experimental results well, were employed to analyze
the efficiency of manual transmission system. In terms of formulas of power losses of each part in the transmission, the
dynamic transmission efficiency model of manual transmission/reducer based on Matlab/Simulink was established. The
efficiency map of each shift of a specific five-speed manual transmission was simulated under new European Driving Cycle
(NEDC). Finally, in terms of simulation results, a new type gearbox was proposed and analyzed, which is capable of
improving transmission efficiency significantly.