Manual transmission, also known as manual gear transmission, is composed of input shaft, shaft shaft and intermediate shaft, and gear on the shaft. Its working principle is to use the hand to change the gear lever to change the gear meshing position in the transmission so as to achieve the purpose of variable speed and twist. The input shaft is also called the first shaft, and its front spline is directly matched with the spline sleeve of the clutch driven disc, thereby transmitting the torque coming from the engine. The gear on the first axis is meshed with the middle shaft gear, so long as the input shaft rotates, the middle shaft and the gears on it also rotate. The output shaft is also known as the second axis, and the shaft has various gear gears. It can be meshed with the intermediate shaft at any time under the action of the manipulating device, so as to change the speed and torque of its own. The driving path of the forward gear of the transmission is: the constant meshing gear from the input shaft to the middle shaft often meshing gear, then the countershaft corresponding to the gear, and finally the second axis corresponding gear. The gear on the reversing shaft can also be moved by the control device, moved on the shaft, meshed with the intermediate shaft gear and the output shaft gear, and output in the opposite direction of rotation. As the input axis of the transmission and the output axis rotate at their respective speed, and when the gear is transformed, the two gears with different rotational speeds are bound to have a impact and damage gear, and a problem of synchronization is needed. Therefore, the synchronizer is used to make the gears to be meshed smoothly at the same speed. There are also some faults in the daily use of transmission, such as shifting difficulties, automatic jumping, abnormal sound, random gear, oil leakage and heat. Here we focus on analyzing the reasons and diagnostic methods of gearshift difficulty.