How to troubleshoot the fault of forklift gear shift rush?

The cpcd5aiiz forklift experienced a strong impact and abnormal noise when shifting gears during operation. This is due to the fact that the vehicle is equipped with a hydraulic shift fixed-axis variable reducer or a loose differential.

When the input shaft of the main reducer was manually rotated, it was found that there was a free rotation clearance of nearly 30 degrees. Therefore, it was determined that the meshing clearance of the main reducer was too large. The main reducer was removed and its clearance was measured to be 0.65mm (the standard value is 0.30-0.50mm). Adjust the position of the bevel tooth so that the meshing clearance between it and the driving bevel gear is 0.35mm. After reassembly and test operation, there was still a gear shifting shock phenomenon and abnormal noise when shifting gears. The degree was only slightly less than before, but the fault remained.

For this purpose, remove the drive shaft again to put the transmission in an unloaded state. Start the engine and repeat the gear shifting, gear pushing and gear shifting tests. It was found that the abnormal noise produced at the moment of gear shifting still existed, and there was a relatively obvious vibration in the transmission. Check the supporting and fixing bolts of the transmission to ensure they are not loose. Judging from this phenomenon, the fault should be inside the transmission. The transmission was disassembled, cleaned and inspected. It was found that the tapered roller bearings of the driving and driven shafts of the reverse and forward gear clutches were loose. By adjusting the bearing to an appropriate clearance by adding or removing gaskets and reassembling it for a test run, the phenomenon of gear shifting impact and abnormal noise was somewhat reduced, but the fault phenomenon still existed.

After such a detailed inspection, the root cause of the fault still cannot be found. So, is there a defect in the design or manufacture of this type of forklift? So, we found forklifts of the same model produced by the same factory and conducted road tests on gear shifting, gear pushing and gear lowering. The results showed that there was a slight gear shifting impact phenomenon in all of them, but the severity was different. Therefore, the focus of identifying the cause of the fault should be placed on the hydraulic control part of the transmission. By referring to the transmission control schematic diagram and parts catalog of this machine, it can be known that the return of the clutch piston is achieved by the preload force of the spring. Therefore, at the moment of gear shifting, there may be an excessive flow of pressure control oil in the main clutch, which quickly overcomes the spring preload force, causing the driving plate and driven plate to engage too quickly and resulting in gear impact. To verify this assumption, certain modifications need to be made to the hydraulic control pipeline. An adjustable throttle valve should be connected in series between the directional control valve and the pistons of each clutch to control the flow rate, so as to achieve a smooth connection.