① Abnormal transmission sound. Because  gear wear is too large, tooth side clearance is too large, meshing clearance of the gear increases during the work, resulting in a certain swimming, collision sound. (2) gear bearing wear overdue, so that axial and transverse clearance becomes larger, the amount of activity at work increases, resulting in abnormal transmission sound,various fastening bolts of the transmission loose, resulting in abnormal transmission sound at work; spline wear of gear and gear shaft can also cause abnormal sound in the transmission. In addition, the lack of lubricating oil, so that  transmission parts produced dry friction, can also emit abnormal sound. The shift is not flexible. main reason is that the change gear works for a long time, which makes the tooth end of the gear burr, leading to the change gear of the transmission is not flexible.