變速箱作為汽車核心傳動部件，正常工況下可靠性較高。但隨著行駛里程增加或操作不當，其零部件磨損、變形加劇，可能引發異響、掛擋異常、跳擋、亂擋、頓挫沖擊、漏油等故障。以下從技術角度解析典型故障：1 變速箱的異常聲響

　　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）現象發動機怠速、變速箱空擋時產生異響，踩下離合器踏板后聲響消失。（2）原因變速箱與發動機安裝同軸度偏差，或殼體形變導致傳動軸線偏移輸入軸前軸承磨損、污染或表面損傷；常嚙合齒輪齒面磨損超限、齒側間隙過大，或存在斷齒；非成對更換齒輪導致嚙合精度不足；軸承松曠、損壞或齒輪軸向間隙超標；撥叉與接合套配合間隙過大。

　　(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掛擋運行異響

　　2. Abnormal noise during gear shifting operation

　　（1）現象入擋位后，車速≥40km/h時出現隨速增大的異常聲響，滑行或低速時減弱。（2）診斷齒輪/軸振動通過殼體共振傳遞，需按擋位特征定位故障源；空擋異響+踩離合消失→常嚙合齒輪嚙合異常；全擋位異響→基礎件（殼體）、軸、齒輪或花鍵形位公差超限；單擋位異響→該擋齒輪副磨損或軸承松曠。

　　(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變速器跳擋

　　3 Transmission Jumping

　　（1）現象行駛中變速桿自動跳回空擋，常見于中高速負荷突變或車身劇烈振動時。（2）原因齒輪/齒套沿齒長方向磨成錐形，產生軸向分力；自鎖裝置（叉軸凹槽、定位球、彈簧）磨損失效；軸系磨損導致齒輪嚙合深度不足，軸向竄動；操縱機構松曠或撥叉變形。（3）診斷1. 掛擋后拆檢齒輪嚙合狀態，若正常則排查換擋機構；2. 撥動變速桿無阻力→自鎖裝置失效（檢查鋼球、凹槽、彈簧）；3. 齒輪未完全嚙合→撥叉磨損/變形需校正或更換；4. 機構正常則檢測齒輪錐度、軸承間隙。

　　(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掛擋困難

　　Difficulty in shifting gears

　　（1）現象掛擋時，不能順利掛入擋位，常發生齒輪撞擊聲。（2）原因機械因素：叉軸彎曲、自鎖/互鎖鋼球卡滯、同步器磨損（錐環螺旋槽磨平、滑塊失效）、輸入軸花鍵損傷；關聯系統：離合器分離不徹底、齒輪油黏度過高或型號不符。

　　(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變速器亂擋

　　5. Improper transmission

　　（1）現象汽車起步掛擋或行駛中換擋，所掛擋與需要擋位不符，或雖然掛入所需擋位但不能退回空擋，或一次掛入兩個擋位。（2）原因變速桿與撥端松曠、撥端內孔磨損超限；互鎖銷磨損導致防錯功能失效；換擋控制器彈簧彈力不足。

　　(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變變速箱過熱

　　6-speed gearbox overheating

　　（1）原因：軸承預緊力過大或裝配過盈量超標；齒輪副嚙合間隙過小導致滑動摩擦加劇；潤滑不足（油量缺失或油液黏度過低）。

　　(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 變速箱漏油

　　7 Transmission oil leakage

　　（1）診斷：

　　(1) Diagnosis:

　　密封系統：襯墊老化、油封失效、螺栓松動；殼體損傷：鑄造缺陷或外力導致裂紋；壓力異常：油液加注過量或通氣孔堵塞。

　　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、故障維修案例

　　2、 Fault repair case

　　1科魯茲轎車3擋極易脫落

　　1 Cruze sedan, 3rd gear is prone to detachment

　　故障現象—輛科魯茲轎車，行駛里程約為10萬千米。該車3擋極易脫落。檢查分析路試發現該車3擋的擋位手感不清晰，入擋后稍一加速就會脫成空擋。車速低時，3擋更難換入。發動機熄火后，3擋換擋正常，但是手感仍然不清晰。發動機怠速運轉時換入3擋，能感到齒輪的同步很吃力，要推住擋桿一段時間才能換入。如果在推住擋桿的同時提高怠速，則比較容易入擋，這說明3擋的同步環已經出現了打滑現象，要借助額外的轉動力矩才能實現齒輪的同步。在這種情況下，決定對變速箱進行解體檢查。

　　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.

　　解體變速箱檢查，發現3擋撥叉末端的尼龍套已經不見了。根據這一現象判斷，同步器已經完全失效了。進一步檢查發現，同步環內圈的紋路已經被磨平，這樣一來，這些紋路就無法切入油膜來為齒輪提供同步扭矩。根據維修手冊的提示，測量同步環與齒輪之間的間隙，發現已經嚴重超差，如下圖所示。分析認為故障原因是不良的駕駛習慣，即駕駛員在換擋時離合器經常分離不徹底，導致同步器過載，從而出現早期磨損。故障排除更換3擋同步環和換擋撥叉，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北京現代名圖掛擋困難

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

　　故障現象：掛擋困難故障診斷：當踩下離合器踏板以后將換擋桿推入倒擋時，換擋桿不能夠順利地推入倒擋，可是當把換擋桿撥到空擋后重新推入倒擋時，換擋桿卻能夠順利地推入倒擋位。按照上述的方法又測試了其他擋位，發現1擋、2擋和3擋也都存在同樣的問題。不過在故障檢查當中，維修人員也發現如果將離合器踏板踩下以后持續保持約5s以上的時間再進行掛擋時，基本上不存在掛擋困難的情況。根據我們對該車故障的檢測，我們初步判斷故障的可能原因如下。① 離合器分離不徹底。② 換擋桿位置調整不當。③ 變速箱油型號不符。④ 變速箱內部故障。

　　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.

　　變速箱油是出廠時充注的原廠變速箱油，所以在變速箱油方面，我們只是檢查了一下變速箱油是否充足，檢查的結果是正常的。然后我們又按照維修手冊的要求檢查了換擋桿的位置，這個也是沒有問題的。考慮到變速箱本身不太可能會出現問題，而且即便是有問題也不可能是倒擋、1擋、2擋和3擋同時出問題。

　　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.

　　所以最后我們把故障原因圈定在了離合器分離不徹底這方面。離合器分離不徹底的原因有兩方面：一方面是離合器操作部分，比如離合器總泵、離合器分泵、離合器分離撥叉；另一方面就是離合器本體部分，比如離合器壓盤或離合器片。于是在接下來的故障檢查當中，按照由簡到難的步驟先后檢查了離合器總泵、離合器分泵，并對離合器分泵進行放氣排油的操作，而且也從外部檢查了離合器分離撥叉的動作，上述這些檢查均未發現有任何問題，最后只能將變速器拆卸下來檢查離合器本體的情況。

　　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.

　　拆下變速箱以后我們發現變速箱輸入軸的齒槽上布滿了銹跡，如圖3-189所示，而與之嚙合的離合器的內花鍵上也同樣是銹跡斑斑，如圖3-190所示。將離合器片裝入變速器輸入軸上，滑動離合器片時發現離合器片的運動并不是很順暢。使用鋼絲刷清除變速箱輸入軸上的銹跡，然后使用除銹劑和銼清潔離合器片內花鍵上的銹跡。完成上述清潔工作后重新裝配變速器，如圖3-191所示，最后再次試車時故障排除。

　　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轎車無法掛擋

　　3 Lavida 2.0MT sedan unable to shift gears

　　故障現象一輛行駛里程約為6萬千米的2015年產朗逸2.0MT轎車，車主反映該車無法掛擋。故障診斷接車后，首先驗證故障現象，操縱換擋手柄，變速箱的確無法掛上擋；拆檢變速箱的換擋操縱機構，發現該車的換擋拉索已經斷裂，更換換擋拉索，裝復變速箱換擋操縱機構后試車，變速箱掛擋正常。但是車開一會，再次出現無法掛擋的故障。再次拆檢變速箱換擋操縱機構，發現新更換上去的換擋拉索再次斷裂，這不可能是換擋拉索的質量問題導致的故障。經過仔細檢查發現該車變速箱的安裝位置和正常車有偏差，從而導致每次換擋操作時換擋拉索均被干涉而斷裂；檢查變速箱的支撐螺栓，發現該車變速箱左側支撐螺栓松動。故障排除按照規定力矩安裝變速箱左側支撐螺栓并更換換擋拉索。

　　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.