The manufacturing quality of synchronizer is not high. If the locking pin is not strong enough and the riveting is not firm, it will easily cause the synchronizer frame to skew, so it is difficult to ensure the clearance between the cone disc and the cone ring. Often in the neutral position, the cone disc and the cone ring are still in contact and burned.

　　②潤滑油質量差。潤滑油中結膠，污物填滿同步器摩擦錐環錐面的齒紋溝槽內，造成摩擦系數下降，同步器失控，所以要定期更換潤滑油。

　　(2) The quality of lubricating oil is poor. The gluing in lubricating oil and dirt filling in the tooth groove of the conical surface of the friction cone ring of the synchronizer cause the friction coefficient to decrease and the synchronizer to lose control, so the lubricating oil should be replaced regularly.

　?、壑虚g軸四檔齒輪與中間軸過盈不夠，產生軸向位移，將中間軸四檔齒輪卡環擠掉，當四檔齒輪定位失準后，壓迫四、五檔同步器碰擦產生高溫后燒毀。

　　(3) The interference between the four gears of the middle shaft and the middle shaft is not enough, resulting in the axial displacement. The four gears of the middle shaft are squeezed out of the clamp ring. When the four gears are misaligned, the four and five gears of the synchronizer are pressed and rubbed to produce high temperature and then burned.

　?、茏兯贀懿嫖恢貌划敚瑢е洛F盤與錐環處于高速摩擦狀態而燒毀。

　　(4) The inappropriate position of the shifting fork causes the cone disc and the cone ring to be burnt down in the state of high-speed friction.

　?、蓠{駛人操作不當。不少汽車駕駛人在空檔熄火滑行，待滑行終了需加速時，不是先打開點火開關起動發動機（利用中間軸旋轉將潤滑油飛濺到錐盤和錐環之間），而是采用直接掛檔，靠錐盤來強行拖動發動機，這樣強大的慣性力矩作用于同步器錐環和鎖銷上，使鎖銷彎曲、錐環變形，破壞錐盤與錐環間隙（一般為0.3一0. 60mm )，錐環長期在惡劣摩擦條件下工作，溫度上升很快，后燒毀。

　　The driver operated improperly. Many automobile drivers skid in neutral stall. When accelerating at the end of skidding, they do not start the engine by turning on the ignition switch (splashing lubricant between the cone disc and the cone ring by the rotation of the middle axle), but by using direct gearing and relying on the cone disc to drive the engine forcefully. Such a strong inertia moment acts on the cone ring and the lock pin of the synchronizer, bending the lock pin and deforming the cone ring. The gap between the cone disc and the cone ring is destroyed (usually 0.3-0.60 mm). The cone ring works under harsh friction conditions for a long time, and the temperature rises rapidly, and finally burns down.