Several common faults and diagnoses of overrunning clutches in loaders

1. When operating at low speed and under heavy load, there is a momentary pause phenomenon

When a loader is operating at low speed and heavy load, if it suddenly makes a "clicking" pause sound, then accelerates and the vehicle continues to move forward, this is the most common early sign of a malfunction in the overrunning clutch. As the usage time increases, this phenomenon will occur more and more frequently during work, and the pause time will also be correspondingly prolonged. The greater the workload, the more one feels a lack of motivation.

2. The vehicle operates normally in second gear, but suddenly loses power

The loader usually works well and runs normally in second gear, but it may suddenly experience weakness in operation. During the inspection, it was found that the hydraulic oil in the transmission had not deteriorated, the oil level met the requirements, the oil bottom filter screen was not clogged, and the shifting pressure was also normal. This indicates that the overrunning clutch has been damaged and failed.

3 The transmission suddenly made an abnormal noise and the vehicle speed dropped sharply

When the loader is traveling at a high speed, a loud mechanical noise suddenly comes from the transmission area. Then, as if it has been braking, the speed drops sharply. At this point, release the accelerator and stop the vehicle. There is no need to shift gears. Let it idle for a while and the noise will disappear. Then, step on the accelerator and the vehicle will return to normal operation. If this phenomenon occurs from time to time, it is due to the jamming of the rollers in the overrunning clutch. The rollers should have been in the non-working position but are now stuck in the working position, causing the output gear of the first stage turbine, which was originally not in operation, and the outer ring gear of the overrunning clutch to work intermittently, resulting in a loud clashing sound from the gears and generating a large braking force at the same time.

4 When starting or shifting gears, the motorcycle responds slowly

During the operation of the loader, the feel and rhythm when shifting gears are normal, and there is no looseness in the gear lever system. The speed change pressure and the response during gear shifting are also normal. However, sometimes the vehicle's response is relatively slow when starting and shifting gears. This is due to the poor engagement and slow locking between the outer ring gear and the inner ring CAM of the overrunning clutch.

5. There is no difference in speed between second gear and first gear

Some loaders work powerfully at low speeds and heavy loads, but the oil temperature of the torque converter rises rapidly, and there is no difference in speed between the second gear and the first gear. This is because the rollers of the overrunning clutch are stuck in the working position, keeping the outer ring gear and the inner ring CAM in a engaged state all the time. That is, the first and second stage turbines are constantly working under a larger load and a lower speed, causing the oil temperature to rise rapidly and the locomotive to travel at a slower speed.

6 Inspection of the overrunning clutch assembly

When inspecting the overrunning clutch assembly, it is generally necessary to first check whether the bearings have fallen off. If any, the parts should be replaced for repair or the assembly should be replaced. If not, the middle input shaft should be braked and the outer ring gear should be turned clockwise and counterclockwise respectively. A good one should be able to rotate clockwise but not counterclockwise. If it can rotate clockwise or counterclockwise, it indicates that it has been damaged. Sometimes it can rotate clockwise but not counterclockwise, and this does not mean it is good. At this point, if the outer ring gear is vibrated a few times to cause a slight change or adjustment in its relative position with the inner ring CAM and rollers, and if it can rotate relatively clockwise or counterclockwise, it indicates that the overrunning clutch has been damaged. If it can only be turned clockwise and there is a loose sound of the rollers during rotation, and it feels loose to the touch, this is also a sign that the overrunning clutch is damaged. The above three types of damage conditions will cause the fault phenomena described in items 1 to 4 above. If it cannot rotate clockwise or counterclockwise, it indicates that the outer ring gear and the inner ring CAM have locked up, and the fifth fault phenomenon mentioned above will occur.

Generally speaking, when inspecting the overrunning clutch assembly based on experience, it is important to pay attention to the working conditions under various working conditions before the disassembly of the loader. Only faults with relatively large and serious damage can be detected. However, faults with poor locking performance but still capable of locking cannot be detected when the loader is also not working well. Certain instruments must be used for inspection. When the performance of a loader is poor due to the damage of the overrunning clutch, the overrunning clutch should be inspected based on the characteristics that its gear shifting pressure, gear shifting feel, and pressure changes during gear shifting are all normal, in combination with the usage conditions of the loader, and a relatively correct inspection conclusion should be made.

The damage of an overrunning clutch is generally manifested as excessive wear or squeezing deformation of the rollers, the inner track of the outer ring gear, and the wedge-shaped surface of the inner ring CAM, which prevents the outer ring gear from locking or getting stuck with the inner ring CAM and thus cannot be separated. The working spring cover is damaged, and the spring breaks, deforms, softens and loses its function, preventing the roller from pressing against the higher position of the wedge-shaped surface of the inner ring CAM and thus failing to play a locking role. The isolation ring is damaged, deformed or loose, causing the rollers and springs to fall off, or preventing the rollers from pressing at the high position of the wedge-shaped surface.