Faults and Analysis of the Rear Axle Differential of ZL50 Loader

First, we analyze the cause of the fault through the fault phenomenon. When the loader is traveling in a straight line, the rear drive axle is normal, but when it is turning, there is a relatively loud noise from the rear drive axle. It is initially judged that the fault may occur in the differential. When the loader travels in a straight line, the wheels on both sides roll the same distance at the same time, and the rotational speeds of the differential housing and the two half shafts are the same. The planetary gears do not rotate on their own axes but only revolve around the differential housing. At this time, the differential does not play a differential role. When the loader turns and travels, the planetary gears not only drive the two half shaft gears to rotate but also rotate around the cross journal. Due to the different resistance reflected by the inner and outer wheels on the planetary gears, the rotational speeds of the two half shafts are not equal. At this time, the differential plays a differential role.

We removed the connecting screws between the rear drive axle and the frame, the main transmission disc screws, the brake oil pipe joints, etc. We lifted the frame with a crane, pushed the rear drive axle and the wheels backward, and drained the gear oil from the rear drive axle and the wheel side reducers on both sides. We found that the gear oil in the rear drive axle was very dirty, with some needle-like and flaky metal shavings in it. It is initially determined that the fault occurred in the differential.

We disassembled the drive axle housing, removed the main transmission, differential, two half shafts and the sun gears of the two wheel-side reducers. After disassembling the differential housing, it was found that the teeth of the four planetary gears and two half shaft gears inside the differential were severely damaged. Of the four planetary gears, only one gasket remains relatively intact, while the rest have worn out. The driving bevel gear, cross shaft and differential housing are severely worn. There were many large and small needle-like and flaky metal debris at the bottom of the drive axle housing, confirming that the fault occurred in the differential.

What caused the malfunction? We asked the operator and inspected other devices. The front and rear axle drive (four-wheel drive) of this ZL50 loader is not easy to combine, and once combined, it is not easy to separate. The operator never checked the gear oil in the rear drive axle. Due to the dirty gear oil in the rear drive axle, the gaskets of the planetary gears wore out, and the clearance between the planetary gears and the two half shaft gears increased. In addition, frequent full-load turning operations in "V", "I", "L", and "T" directions were carried out. This caused the teeth of the planetary gear and the two half shaft gears to be damaged due to excessive clearance during high-speed rotation. The damaged metal debris entered the bottom and the gear oil inside the rear drive axle, causing severe wear on the driving bevel gear, cross shaft and differential housing during rotation. When traveling in a straight line, the four planetary gears and two half shaft gears inside the differential revolve around the differential housing without rotating on their own axes, so the rear drive axle makes no noise. When turning and moving, the four planetary gears that mesh with the two half shaft gears encounter unequal resistance and start to rotate on their own. Due to their excessive clearance and the damage of the meshing teeth, noise is produced. The more severe the damage, the greater the noise.

We thoroughly cleaned the rear drive axle housing and other parts, replaced the differential and main transmission, reinstalled the two half shafts, the sun gear gears of the two wheel-side reducers and the drive axle housing, and updated the gear oil in the rear drive axle and the two wheel-side reducers. After the test run following the assembly, the above-mentioned noise faults were immediately eliminated.