变速箱作为汽车核心传动部件，正常工况下可靠性较高。但随着行驶里程增加或操作不当，其零部件磨损、变形加剧，可能引发异响、挂挡异常、跳挡、乱挡、顿挫冲击、漏油等故障。以下从技术角度解析典型故障：1 变速箱的异常声响

　　As the core transmission component of automobiles, the gearbox has high reliability under normal operating conditions. But with the increase of driving mileage or improper operation, the wear and deformation of its components may intensify, which may cause abnormal noise, gear shifting abnormalities, gear jumping, derailment, jerking impact, oil leakage and other faults. The following is a technical analysis of typical faults: 1. Abnormal noise from the gearbox

　　（1）现象发动机怠速、变速箱空挡时产生异响，踩下离合器踏板后声响消失。（2）原因变速箱与发动机安装同轴度偏差，或壳体形变导致传动轴线偏移输入轴前轴承磨损、污染或表面损伤；常啮合齿轮齿面磨损超限、齿侧间隙过大，或存在断齿；非成对更换齿轮导致啮合精度不足；轴承松旷、损坏或齿轮轴向间隙超标；拨叉与接合套配合间隙过大。

　　(1) The phenomenon is that there is abnormal noise when the engine is idling and the gearbox is in neutral, and the sound disappears when the clutch pedal is pressed. (2) The reason is that the coaxiality deviation between the gearbox and engine installation, or the deformation of the housing, causes the transmission axis to shift and the front bearing of the input shaft to wear, contaminate or damage the surface; The tooth surface wear of the regularly meshed gear exceeds the limit, the tooth side clearance is too large, or there are broken teeth; Non paired gear replacement leads to insufficient meshing accuracy; Loose or damaged bearings or excessive axial clearance of gears; The clearance between the fork and the joint sleeve is too large.

　　2挂挡运行异响

　　2. Abnormal noise during gear shifting operation

　　（1）现象入挡位后，车速≥40km/h时出现随速增大的异常声响，滑行或低速时减弱。（2）诊断齿轮/轴振动通过壳体共振传递，需按挡位特征定位故障源；空挡异响+踩离合消失→常啮合齿轮啮合异常；全挡位异响→基础件（壳体）、轴、齿轮或花键形位公差超限；单挡位异响→该挡齿轮副磨损或轴承松旷。

　　(1) After entering gear, there is an abnormal sound that increases with speed when the vehicle speed is ≥ 40km/h, and decreases when coasting or at low speeds. (2) Diagnosing the transmission of gear/shaft vibration through shell resonance requires locating the fault source based on gear characteristics; Neutral gear noise+disappearance of clutch pedal → abnormal meshing of normally engaged gears; All gear abnormal noise → The tolerance of the basic components (housing), shaft, gear or spline exceeds the limit; Single gear abnormal noise → The gear pair of this gear is worn or the bearing is loose.

　　3变速器跳挡

　　3 Transmission Jumping

　　（1）现象行驶中变速杆自动跳回空挡，常见于中高速负荷突变或车身剧烈振动时。（2）原因齿轮/齿套沿齿长方向磨成锥形，产生轴向分力；自锁装置（叉轴凹槽、定位球、弹簧）磨损失效；轴系磨损导致齿轮啮合深度不足，轴向窜动；操纵机构松旷或拨叉变形。（3）诊断1. 挂挡后拆检齿轮啮合状态，若正常则排查换挡机构；2. 拨动变速杆无阻力→自锁装置失效（检查钢球、凹槽、弹簧）；3. 齿轮未完全啮合→拨叉磨损/变形需校正或更换；4. 机构正常则检测齿轮锥度、轴承间隙。

　　(1) The phenomenon of the gear lever automatically jumping back to neutral during driving is common when there is a sudden change in load at medium to high speeds or when the vehicle body vibrates violently. (2) The reason is that the gear/sleeve is ground into a cone shape along the tooth length direction, resulting in axial force distribution; The self-locking device (fork groove, positioning ball, spring) has worn out and failed; Shaft wear leads to insufficient gear meshing depth and axial displacement; The control mechanism is loose or the shift fork is deformed. (3) Diagnosis 1 After shifting gears, check the meshing status of the gears. If it is normal, investigate the shifting mechanism; 2. There is no resistance when shifting the gear lever → The self-locking device fails (check the steel ball, groove, and spring); 3. The gear is not fully engaged → the fork needs to be corrected or replaced due to wear/deformation; If the mechanism is normal, check the gear taper and bearing clearance.

　　4挂挡困难

　　Difficulty in shifting gears

　　（1）现象挂挡时，不能顺利挂入挡位，常发生齿轮撞击声。（2）原因机械因素：叉轴弯曲、自锁/互锁钢球卡滞、同步器磨损（锥环螺旋槽磨平、滑块失效）、输入轴花键损伤；关联系统：离合器分离不彻底、齿轮油黏度过高或型号不符。

　　(1) When shifting gears, it is difficult to smoothly shift into the gear, and gear collision sounds often occur. (2) Reasons for mechanical factors: fork shaft bending, self-locking/interlocking steel ball jamming, synchronizer wear (cone ring spiral groove worn flat, slider failure), input shaft spline damage; Associated system: Incomplete clutch disengagement, high viscosity of gear oil, or inconsistent model.

　　5变速器乱挡

　　5. Improper transmission

　　（1）现象汽车起步挂挡或行驶中换挡，所挂挡与需要挡位不符，或虽然挂入所需挡位但不能退回空挡，或一次挂入两个挡位。（2）原因变速杆与拨端松旷、拨端内孔磨损超限；互锁销磨损导致防错功能失效；换挡控制器弹簧弹力不足。

　　(1) Phenomenon: When the car starts to shift gears or shifts gears while driving, the gear engaged does not match the required gear, or although the required gear is engaged, it cannot return to neutral, or two gears are engaged at once. (2) The reason is that the gear lever and the dial end are loose, and the wear of the dial end inner hole exceeds the limit; Wear of interlocking pins leads to the failure of error prevention function; The spring elasticity of the shift controller is insufficient.

　　6变变速箱过热

　　6-speed gearbox overheating

　　（1）原因：轴承预紧力过大或装配过盈量超标；齿轮副啮合间隙过小导致滑动摩擦加剧；润滑不足（油量缺失或油液黏度过低）。

　　(1) Reason: Excessive pre tightening force of bearings or excessive interference during assembly; Insufficient meshing clearance of gear pairs leads to increased sliding friction; Insufficient lubrication (lack of oil or low viscosity of oil).

　　7 变速箱漏油

　　7 Transmission oil leakage

　　（1）诊断：

　　(1) Diagnosis:

　　密封系统：衬垫老化、油封失效、螺栓松动；壳体损伤：铸造缺陷或外力导致裂纹；压力异常：油液加注过量或通气孔堵塞。

　　Sealing system: gasket aging, oil seal failure, bolt loosening; Shell damage: Casting defects or cracks caused by external forces; Abnormal pressure: Excessive oil filling or blocked vent hole.

　　二、故障维修案例

　　2、 Fault repair case

　　1科鲁兹轿车3挡极易脱落

　　1 Cruze sedan, 3rd gear is prone to detachment

　　故障现象—辆科鲁兹轿车，行驶里程约为10万千米。该车3挡极易脱落。检查分析路试发现该车3挡的挡位手感不清晰，入挡后稍一加速就会脱成空挡。车速低时，3挡更难换入。发动机熄火后，3挡换挡正常，但是手感仍然不清晰。发动机怠速运转时换入3挡，能感到齿轮的同步很吃力，要推住挡杆一段时间才能换入。如果在推住挡杆的同时提高怠速，则比较容易入挡，这说明3挡的同步环已经出现了打滑现象，要借助额外的转动力矩才能实现齿轮的同步。在这种情况下，决定对变速箱进行解体检查。

　　Fault phenomenon - a Cruze sedan with a mileage of approximately 100000 kilometers. The third gear of the car is prone to falling off. During the inspection and analysis of the road test, it was found that the third gear of the car does not have a clear feel. After entering gear, it will shift to neutral as soon as it accelerates slightly. When the speed is low, it is more difficult to shift into third gear. After the engine is turned off, shifting to third gear is normal, but the feel is still unclear. When the engine is idling and shifting to third gear, you can feel that the synchronization of the gears is very difficult, and you need to push the gear lever for a period of time before shifting in. If the idle speed is increased while pushing the gear lever, it is easier to shift into gear, indicating that the synchronizing ring of third gear has slipped and requires additional rotational torque to achieve gear synchronization. In this situation, it is decided to conduct a disassembly inspection on the gearbox.

　　解体变速箱检查，发现3挡拨叉末端的尼龙套已经不见了。根据这一现象判断，同步器已经完全失效了。进一步检查发现，同步环内圈的纹路已经被磨平，这样一来，这些纹路就无法切入油膜来为齿轮提供同步扭矩。根据维修手册的提示，测量同步环与齿轮之间的间隙，发现已经严重超差，如下图所示。分析认为故障原因是不良的驾驶习惯，即驾驶员在换挡时离合器经常分离不彻底，导致同步器过载，从而出现早期磨损。故障排除更换3挡同步环和换挡拨叉，故障排除。

　　Upon disassembling the gearbox for inspection, it was found that the nylon sleeve at the end of the 3rd gear shift fork was missing. Based on this phenomenon, it can be concluded that the synchronizer has completely failed. Further inspection revealed that the patterns on the inner ring of the synchronizing ring had been smoothed out, making it impossible for these patterns to penetrate the oil film and provide synchronizing torque to the gear. According to the instructions in the maintenance manual, the gap between the synchronizing ring and the gear was measured and it was found to be severely out of tolerance, as shown in the following figure. Analysis suggests that the cause of the malfunction is due to poor driving habits, where the clutch often fails to fully disengage when shifting gears, leading to overload of the synchronizer and early wear and tear. Troubleshooting: Replace the 3rd gear synchronizing ring and shift fork to resolve the issue.

　　2北京现代名图挂挡困难

　　2. Difficulty in shifting gears in Beijing Hyundai's famous map

　　故障现象：挂挡困难故障诊断：当踩下离合器踏板以后将换挡杆推入倒挡时，换挡杆不能够顺利地推入倒挡，可是当把换挡杆拨到空挡后重新推入倒挡时，换挡杆却能够顺利地推入倒挡位。按照上述的方法又测试了其他挡位，发现1挡、2挡和3挡也都存在同样的问题。不过在故障检查当中，维修人员也发现如果将离合器踏板踩下以后持续保持约5s以上的时间再进行挂挡时，基本上不存在挂挡困难的情况。根据我们对该车故障的检测，我们初步判断故障的可能原因如下。① 离合器分离不彻底。② 换挡杆位置调整不当。③ 变速箱油型号不符。④ 变速箱内部故障。

　　Fault phenomenon: Difficulty shifting. Fault diagnosis: When the clutch pedal is pressed and the shift lever is pushed into reverse, it cannot be smoothly pushed into reverse. However, when the shift lever is shifted to neutral and pushed back into reverse, it can be smoothly pushed into reverse. According to the above method, other gears were tested and it was found that the same problem existed in 1st, 2nd, and 3rd gears. However, during the fault inspection, the maintenance personnel also found that if the clutch pedal is pressed and held for about 5 seconds or more before shifting, there is basically no difficulty in shifting. Based on our inspection of the vehicle malfunction, we have preliminarily determined the possible causes of the problem as follows. ① The clutch is not completely disengaged. ② Improper adjustment of the gear lever position. ③ The transmission oil model does not match. ④ Internal gearbox malfunction.

　　变速箱油是出厂时充注的原厂变速箱油，所以在变速箱油方面，我们只是检查了一下变速箱油是否充足，检查的结果是正常的。然后我们又按照维修手册的要求检查了换挡杆的位置，这个也是没有问题的。考虑到变速箱本身不太可能会出现问题，而且即便是有问题也不可能是倒挡、1挡、2挡和3挡同时出问题。

　　The transmission oil is the original transmission oil filled at the factory, so in terms of transmission oil, we only checked whether the transmission oil is sufficient, and the inspection result is normal. Then we checked the position of the gear lever according to the requirements of the maintenance manual, and there was no problem with it. Considering that the gearbox itself is unlikely to have a problem, and even if there is a problem, it cannot be caused by reverse, 1st, 2nd, and 3rd gears simultaneously.

　　所以最后我们把故障原因圈定在了离合器分离不彻底这方面。离合器分离不彻底的原因有两方面：一方面是离合器操作部分，比如离合器总泵、离合器分泵、离合器分离拨叉；另一方面就是离合器本体部分，比如离合器压盘或离合器片。于是在接下来的故障检查当中，按照由简到难的步骤先后检查了离合器总泵、离合器分泵，并对离合器分泵进行放气排油的操作，而且也从外部检查了离合器分离拨叉的动作，上述这些检查均未发现有任何问题，最后只能将变速器拆卸下来检查离合器本体的情况。

　　So in the end, we identified the cause of the malfunction as incomplete clutch disengagement. There are two reasons for incomplete clutch disengagement: one is the clutch operation part, such as the clutch master cylinder, clutch slave cylinder, and clutch disengagement fork; On the other hand, it is the clutch body part, such as the clutch pressure plate or clutch plate. So in the following troubleshooting, the clutch master cylinder and clutch slave cylinder were checked in order of difficulty, and the clutch slave cylinder was operated to release air and oil. The action of the clutch release fork was also checked externally, and no problems were found. Finally, the transmission could only be disassembled to inspect the condition of the clutch body.

　　拆下变速箱以后我们发现变速箱输入轴的齿槽上布满了锈迹，如图3-189所示，而与之啮合的离合器的内花键上也同样是锈迹斑斑，如图3-190所示。将离合器片装入变速器输入轴上，滑动离合器片时发现离合器片的运动并不是很顺畅。使用钢丝刷清除变速箱输入轴上的锈迹，然后使用除锈剂和锉清洁离合器片内花键上的锈迹。完成上述清洁工作后重新装配变速器，如图3-191所示，最后再次试车时故障排除。

　　After removing the gearbox, we found that the tooth grooves on the input shaft of the gearbox were covered with rust, as shown in Figure 3-189, and the internal splines of the clutch that engaged with it were also stained with rust, as shown in Figure 3-190. When installing the clutch plate onto the transmission input shaft, it was found that the movement of the clutch plate was not very smooth when sliding it. Use a wire brush to remove rust from the input shaft of the gearbox, and then use rust remover and file to clean the rust on the splines inside the clutch disc. After completing the above cleaning work, reassemble the transmission as shown in Figure 3-191, and finally troubleshoot the problem when testing again.

　　3朗逸2.0MT轿车无法挂挡

　　3 Lavida 2.0MT sedan unable to shift gears

　　故障现象一辆行驶里程约为6万千米的2015年产朗逸2.0MT轿车，车主反映该车无法挂挡。故障诊断接车后，首先验证故障现象，操纵换挡手柄，变速箱的确无法挂上挡；拆检变速箱的换挡操纵机构，发现该车的换挡拉索已经断裂，更换换挡拉索，装复变速箱换挡操纵机构后试车，变速箱挂挡正常。但是车开一会，再次出现无法挂挡的故障。再次拆检变速箱换挡操纵机构，发现新更换上去的换挡拉索再次断裂，这不可能是换挡拉索的质量问题导致的故障。经过仔细检查发现该车变速箱的安装位置和正常车有偏差，从而导致每次换挡操作时换挡拉索均被干涉而断裂；检查变速箱的支撑螺栓，发现该车变速箱左侧支撑螺栓松动。故障排除按照规定力矩安装变速箱左侧支撑螺栓并更换换挡拉索。

　　Fault phenomenon: A 2015 Lavida 2.0MT sedan with a mileage of about 60000 kilometers was reported by the owner to be unable to shift gears. After receiving the vehicle for fault diagnosis, the first step is to verify the fault phenomenon. By operating the shift lever, the gearbox indeed cannot shift into gear; Upon disassembling and inspecting the shift control mechanism of the gearbox, it was found that the shift cable of the vehicle had been broken. The shift cable was replaced, and after reinstalling the gearbox shift control mechanism, a test drive was conducted, and the gearbox engaged normally. But after driving for a while, the fault of not being able to shift gears occurred again. Upon re inspection of the gearbox shift control mechanism, it was found that the newly replaced shift cable had broken again, which could not have been caused by a quality issue with the shift cable. After careful inspection, it was found that there was a deviation between the installation position of the gearbox of the car and the normal car, which caused the shift cable to be interfered with and broken during each shift operation; Checked the support bolts of the gearbox and found that the left support bolt of the gearbox was loose. Troubleshooting: Install the left support bolt of the gearbox according to the specified torque and replace the shift cable.