A method of monitoring at least one gear of a transmission is in operation

A method of monitoring at least one gear (1) of a transmission comprising the steps in operation - receiving a number of images each operating in a plurality of positions of the transmission characteristic, - generating at least one averaging the reference image (47) of a number of operation images, - generating at least one difference image (52, 53, 54) of at least one operating image and a reference image averaging (47) at mutually corresponding positions of the gear wheel (1) and - evaluating the difference image (52, 53, 54) or a set of difference images (52, 53, 54).