During the maintenance service, we found that the inter axle differential of individual users was burned, and it continued to burn after replacing the new differential. In severe cases, the planetary gear and the spider are even completely sintered together. There are two main reasons for the burning of the inter axle differential: one is the lack of oil, and the other is the wrong speed ratio between the middle axle and the rear axle of double bridge.
Splash lubrication is adopted for the middle axle main reducer and transition transmission box, and the position of the inter axle differential is the highest. Therefore, the lubrication condition of the inter axle differential is poor. A slight lack of oil will threaten the inter axle differential. When the new vehicle is refueled or the gear oil is replaced, the new oil must be filled through the filler on the inter axle differential housing until the oil level reaches the inspection port of the intermediate axle transition box.
During the service, we also found that individual users did not pay attention to the speed ratio of the original vehicle when replacing the driving and passive bevel gears of the middle axle or rear axle separately, so that the speed ratio of the driving and passive bevel gears replaced by the middle axle or rear axle is different from that of the original vehicle. (the installation dimensions of driving and driven bevel gears with different speed ratios are the same). This will cause the difference in the speed ratio between the middle axle and the rear axle, resulting in the high-speed differential rotation of the inter axle differential during driving. In addition, the poor lubrication condition of the differential itself will soon burn the differential.
Therefore, when replacing the driving and passive bevel gears, it must be noted that the number of teeth is the same as that of the old driving and passive bevel gears of the original vehicle.
When finding the abnormal sound of the drive axle, first judge whether it is the abnormal sound of the middle axle or the rear axle. Then judge the basic part of the abnormal sound. In particular, pay special attention to the sudden obvious abnormal response, and check it immediately. Check the parts with abnormal noise. Jack up the middle axle (or rear axle) with a kilo, start the engine and shift to the speed gear to make the jacked axle rotate slowly and observe the parts with abnormal noise. During this operation, you must pay attention to safety and take insurance measures.
The abnormal noise of the medium bridge is mainly caused by the following reasons:
1) The fixing bolt of the driven bevel gear is dropped or loose
When assembling the passive bevel gear, the connecting bolts are not glued and the torque is not enough, so that the bolts are loose or even completely fall off after driving for a short time. This abnormal noise is often sudden, irregular and loud. At this time, it can no longer be driven forcibly, and it must be disassembled and inspected.
When repairing and replacing the driven bevel gear, loctite 262 thread locking compound must be applied to the thread of the connecting bolt and tightened according to the specified torque.
2) Gear damage
During operation, a tooth part is broken due to various reasons. This abnormal noise is also sudden and obvious, so it should be disassembled and inspected immediately.
3) Bearing loose
There are 7 bearings in the medium bridge, and the abnormal noise caused by the scattered bearings is also obvious. The parts with abnormal noise should be diagnosed and then disassembled for inspection.
4) Differential lock engagement sleeve in series
The loose flower cap of the meshing sleeve of the inter wheel differential lock makes the meshing sleeve move in series, which will produce the sound of collision between the two meshing sleeves. The inter axle differential locking pin will also produce a knocking sound. This abnormal sound is also the sound of irregular mechanical impact.
5) Differential gear burned
Obvious noise will be caused by ablation or tooth damage of planetary gear and axle shaft gear of inter wheel differential and inter axle differential.
The above noise caused by mechanical damage is often sudden, and the abnormal noise is obvious. In case of such abnormal response, disassemble it immediately and stop driving, otherwise it will cause more serious consequences.
6) Continuous noise, and this continuous noise increases with the increase of load and operating speed
This abnormal noise is often caused by bearing pitting, gear wear and strain, too small or too large gear clearance, deviation of bevel gear tooth surface contact part, etc.
Although this abnormal noise is not terrible, it should also be disassembled, inspected and repaired in serious cases, otherwise the fault will expand.
When the conical driving and driven gears are replaced, this abnormal noise indicates that the gear clearance or the thickness of the installation distance adjusting gasket is incorrect, so that the contact between the two tooth surfaces is not in the proper position. The active and passive bevel gears are ground in pairs. Therefore, if a pair of matching gears are not replaced, this abnormal noise will obviously occur and cannot be eliminated.
When repairing and disassembling the driving and driven bevel gears, the installation distance adjusting gasket shall be kept well, and the original gasket must be reinstalled during reassembly, otherwise the meshing noise of the driving and driven gears will also be caused due to the deviation of the adjusting gasket.
7) The car makes no abnormal noise during normal driving, but there is a “buzzing” noise when decelerating and removing oil, which is generally caused by the tensile injury or pitting corrosion on the back of the gear. The slight noise is irrelevant to the overall situation, and it should also be disassembled and inspected in case of serious problems.
8) The gear clearance is too large. The spline shafts and holes are loose. When accelerating or starting, there will be a “clatter” sound, and there is an obvious feeling of looseness.
There may be three reasons for bridge heating: excessive or lack of lubricating oil, and excessive bearing preload.
Lack of oil and lack of lubrication will make the parts hot. Excessive lubricating oil will also cause overheating. If the preload of differential support bearing and driving gear shaft support bearing is too large, overheating will also occur· The latter should be solved by adjusting the shim thickness.
d. Oil leakage
There are other factors besides the oil seal itself. For example, some users reported that there was an oil leak in a certain part, and the replacement of a new oil seal still did not solve the problem. This shows that the oil leakage is not caused by the oil seal itself. First, check whether the air vent of axle housing or transition box is unblocked. If the vent hole is blocked, the heat generated by the operation of the machine will expand the air and generate pressure, forcing the lubricating oil to squeeze out from the oil seal. Oil leakage caused by loose outer ring and seat hole of oil seal is often ignored. The solution is to wipe the outer ring of the oil seal and the seat hole before installing the oil seal, apply loctite 603 cylindrical retaining glue on the outer ring of the oil seal, and then drive the oil seal in.
e. Tire grinding
There are many problems in grinding tires, such as deformation of steel ring, looseness of shaft head bearing, and large difference in air pressure of double row tires. However, another important factor of double axle grinding tire is bridge dislocation.
The balance shaft bushing of the double axle is worn and loose, the rubber support of the balance suspension thrust rod is damaged, and the welding between the balance thrust rod support and the axle housing will cause the dislocation of the axle.
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