①同步器制造质量不高。如锁销强度不足，铆接不牢固，容易造成同步器架歪斜，这样难以保证锥盘和锥环之间的间隙，往往在空档位置时，锥盘与锥环仍接触而烧损。
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润滑油质量差。润滑油中结胶，污物填满同步器摩擦锥环锥面的齿纹沟槽内，造成摩擦系数下降，同步器失控，所以要定期更换润滑油。
(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.
③中间轴四档齿轮与中间轴过盈不够，产生轴向位移，将中间轴四档齿轮卡环挤掉，当四档齿轮定位失准后，压迫四、五档同步器碰擦产生高温后烧毁。
(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.
④变速拨叉位置不当，导致锥盘与锥环处于高速摩擦状态而烧毁。
(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.
⑤驾驶人操作不当。不少汽车驾驶人在空档熄火滑行，待滑行终了需加速时，不是先打开点火开关起动发动机（利用中间轴旋转将润滑油飞溅到锥盘和锥环之间），而是采用直接挂档，靠锥盘来强行拖动发动机，这样强大的惯性力矩作用于同步器锥环和锁销上，使锁销弯曲、锥环变形，破坏锥盘与锥环间隙（一般为0.3一0. 60mm )，锥环长期在恶劣摩擦条件下工作，温度上升很快，后烧毁。
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.
