Abstract: It is well known that the transmission-case gears in an automobile driveline can be the source of noise. This paper describes the results of an experimental study to evaluate the relationship between geometrical gearing errors and gear noises. The inputs in a correlation program come from two sources, namly gear noise spectrum analysis at fixed rotating speed and the single flank composite checking error chart. A relationship between these tests may be established by some mathematical means. Regression analysis indicats, that the correlation between these two input variables, I. E. the readings of single flank tooth-to-tooth composite variation and gear sound pressure level, can not established. But the single flank composite checking curve form conforms closely with the gear sound pressure level. Different error-curve-form causes different gear sound pressure level effect. Hence, by appropriate control over gear error-curve-form, an effective control over gear noise in the manufacture process can be achieved. With introduction of this method, the gear sound pressure level can be decreased about 2～3 db in comparison with the conventional technique used in manufacture process which controls the gear noise with master gears.