The noise control of manual transmission is one of the difficulties of automotive noise control. The noise behavior of a five gears manual transmission is tested based on a low-noise test bench. Then spectral analysis, order analysis and coherence analysis are used to identify the main noise sources of the transmission. The analysis reveals some conclusions. The vibration of transmission is mainly caused by the mesh of shift gears and main reduction gears. The severe vibration caused by gear mesh under high speed operating conditions is relevant to the bending of gear shaft and the modes of gears. Under high speed conditions of fifth gear, the noise is mainly caused by the vibration of a small part of the transmission box. Some measures should be taken to control the vibration of this part. The conclusions provide the experimental support for the optimization and design of low-noise transmissions.