Common fault diagnosis
The transmission generally does not fail, but with the increase of mileage and abnormal operation, the wear and deformation of its parts will increase, and there will be abnormal noise, difficulty in shifting, skipping, random shifting, heat, etc. Oil leaks, etc.1. The abnormal sound of the transmission
(1) Situation
The engine is idling, the transmission is in neutral, and the noise disappears when the clutch pedal is depressed.
(2) Reason
① When the transmission and the engine are installed, the centerline of the crankshaft and the first shaft of the transmission is not concentric, or the transmission case is deformed.
② The front bearing of the second shaft is worn, dirty, and fluffed.
③ The gears of the transmission are often worn, the backlash is too large, or the teeth of individual gears are broken.
④ The constant meshing gears are not replaced in pairs, and the meshing is poor.
⑤ The bearing is loose and damaged, and the axial clearance of the gear is large.
⑥ The clearance between the fork and the joint sleeve is too large.
2. Beep after shifting
(1) Situation
The transmission beeps when it is in gear. When the car is driving at a speed of more than 40km/h, it makes an abnormal sound, and the faster the speed is, the louder the sound is, and the sound decreases or disappears when the car is coasting or at low speed.
(2) Reason
The bending deformation of the shaft, the spline of the shaft and the sliding gear hub are loose. Improper gear meshing, or loose bearings. The joints of the operating mechanism are loose, and the shift fork is deformed. The matching clearance of the main and driven bevel gears is too large.
(3) Diagnosis
The sound of the transmission starts from the vibration of the gear or shaft and other sound sources, and then spreads to the transmission case wall to generate resonance. The diagnosis steps are as follows:
① The engine is running at idling speed, and the transmission has abnormal noise when it is in neutral gear. The noise disappears after depressing the clutch pedal.
② The transmission has noises in all gears, mostly due to the wear of the basic parts, shafts, gears, and splines, which causes the shape and position error to exceed the limit.
③ When a certain gear is engaged, and the sound is serious, it means that the gear of this gear is seriously worn.
3. Transmission jump
(1) Situation
When the car is running, the gear lever automatically jumps back to the neutral position (generally, it usually occurs when the load changes suddenly at medium and high speed or when the car vibrates violently).
(2) Reason
① The gears or gear sleeves of the transmission are worn excessively and are ground into a cone along the length of the teeth.
② The groove of the shifting fork shaft and the positioning ball are worn, and the positioning spring is too soft or broken, which makes the self-locking device fail.
③ The transmission shaft and bearing are worn and loose or the axial clearance is too large, so that the gear meshing is insufficient when the shaft rotates, and the jumping and axial movement occur.
④ The control mechanism is deformed and loose, so that the gear meshing at the tooth length position is insufficient.
(3) Diagnosis
① When a certain gear is found to be skipped, still hang the shift lever in this gear, and then remove the transmission cover to check the gear meshing condition. If the meshing is good, the shifting mechanism should be checked.
② Push the shift lever by hand, if there is no resistance or very little resistance, it means that the self-locking device fails. Check whether the grooves on the self-locking steel ball and the shift fork shaft are too worn, and whether the self-locking steel ball spring is too soft or broken. If so, it should be replaced.
③ If the gears are not fully meshed, check whether the fork is worn or deformed, and correct it if it is bent.
④ If the shifting mechanism is good, check whether the gear is ground into a conical shape and whether the bearing is loose. If necessary, it should be removed for repair or replacement.
4. Difficulty in gear
(1) Situation
When the gear is engaged, the gear cannot be smoothly engaged, and the sound of gear collision often occurs.
(2) Reason
The shift fork shaft is bent and deformed. Self-locking or interlocking steel rings are broken, rough and stuck. Improperly adjusted or damaged shift linkage. Synchronizer is worn or defective. The transmission shaft is bent and deformed or the splines are damaged. In addition to transmission failure, incomplete clutch separation and inconsistent gear oil specifications will also cause difficulty in shifting.
(3) Diagnosis
① Check whether the shift fork shaft is bent and deformed, and whether the self-locking and interlocking steel balls are damaged and whether the spring is too hard.
② Check whether the operating mechanism is deformed or stuck.
③ If the above inspection is normal, check whether it is damaged. Mainly check whether the synchronizer is falling apart, whether the helical groove of the inner cone surface of the synchronizer ring is worn, whether the slider is worn, and whether the spring force is too soft.
④ If the synchronizer is normal, check whether the first shaft of the transmission is bent and whether its splines are worn out.
5. Transmission out of gear
(1) Situation
When the car starts to engage in gear or shifts while driving, the engaged gear does not match the required gear, or although the required gear is engaged but cannot be returned to neutral, or two gears are engaged at a time.
(2) Reason
The shifting lever and the shifting end of the shifting lever are loose, damaged, or the inner hole of the shifting end of the shifting lever is too worn. The spring compression of the transmission controller does not meet the specified requirements. The interlock pin of the shift slider is too worn and loses its interlock function.
(3) Diagnosis
① If the shift lever can swing freely and can make a circle, the clamp pin is broken or lost.
② When the gear shift lever is slightly deviated from the position, an unnecessary gear will be mounted, which is because the working surface of the shifting end of the shift lever is too worn.
③ If two gears can be engaged at the same time, it is caused by the failure of the interlock mechanism.
6. The transmission is hot
(1) Situation: After the car runs for a certain distance, it feels hot when touching the transmission with hands.
(2) Reason: The bearing assembly is too tight. Gear meshing clearance is too small. Lack of gear oil or gear oil viscosity too low.
(3) Diagnosis: It should be excluded by checking the fever part by item.
7. Transmission oil leak
(1) Condition: The gear oil in the transmission leaks out from the bearing cap or the joint.
(2) Reason: The sealing gasket of each part of the transmission is poorly sealed, the oil seal is damaged or the fastening bolts are loose. The transmission case is broken. Too much gear oil. Blocked transmission oil drain bolt or vent hole.
(3) Diagnosis: The cause of oil leakage can be diagnosed according to the location of the oil stain.
