The contribution o fgear tooth flank surface micro-finish on gear noise has not yet been taken into consideration. This paper is devoted to study the simultaneous effect of tooth roughness and lubricant viscosity on automotive gear vibrations.The vibrations performances were evaluated on an instrumented test rig under both dry and wet conditions. A non-destructive replication technique coupled to 3D optical measures was used to acquire the flanks topographies,which were characterized using multiscale decomposition. A three-dimensional finite element simulation of a helical gear was performed to assess the micro-scales impact on gear noise.Numerical representative surfaces morphologies were introduced into the simulation and compared through the transmission error calculation. Results have shown gear noise dependence on tooth finishing processes.