In recent years, there is a trend that lower gear noise levels are demanded for drivers to avoid annoyance and fatigue during operation. For the manual transaxle, meshing transmission error (T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the various interaction analysis of gear tooth profile and lead crowning modification, and the prediction of transmission error under the loaded torques for the 3rd gear pairs of two proposalsin the manual transaxle. And transmission error, root stress and contact stress are also calculated and compared before and after tooth micro-modification under one torque. At last, the gear whine noise of the 3rd gear in WOT (Wide Open Throttle) and the coasting operation condition is investigated and compared between the two proposals. The simulation and test show that the transmission error and contact stress under the loaded torque can be minimized by the appropriate tooth modification. It is a good approach which the simulated result is used to improve the design in order to minimize the radiation gear whine noise.