1) Difficult to shift. The gearshift difficulty caused by gearbox is usually caused by excessive wear or deformation of the fork. The only solution is to replace the fork with a new one. Because this kind of fault has certain hidden danger in the operation of agricultural machinery, once such fault is found, the agricultural manipulator should solve it as soon as possible [3].

2) Automatic out of gear. Excessive wear of the fork, weakened spring force of the fork shaft, serious wear of the spline shaft and gear, looseness or deformation of the auxiliary variable speed connecting rod, etc. will cause the problem of automatic shifting off. As the difficulty of automatic shifting is the same as that in the front, there is a big hidden danger in the operation of agricultural machinery, so it should be eliminated in time; the corresponding solutions to automatic shifting are: replace the new fork, replace the new fork spring, replace the new spline shaft and gear, adjust the tightness of the auxiliary variable-speed connecting rod and carry out the straightening treatment.

3) The transmission is hot. The common causes of excessive friction include: the clearance between variable speed bearings or gears is too small, the amount of lubricating oil does not meet the standard, and the quality of lubricating oil does not meet the standard; the corresponding solutions are: adjust the clearance between variable speed bearings and gears according to the instructions, adjust the amount of lubricating oil to make the liquid level meet the specified value, and replace the lubricating oil of the brand designated by the original factory.

4) There is noise during operation. Similar to clutch running noise, gearbox running noise is also caused by component damage or excessive wear. The common causes include: serious or damaged bearing or gear wear, excessive wear caused by gear mismatch, excessive or damaged spline shaft wear, insufficient lubricating oil consumption, etc.; the corresponding solution is to replace the excessively worn or damaged bearing, gear, spline shaft, etc Adjust the distance between gears to make them fit, add the amount of lubricating oil, etc.