For fast gearbox, most of the friends of truck house may have a certain understanding and use, but because of different models, many friends do not really use it reasonably according to the correct operation. How to shift gears and how to use them often appear on the forum. In fact, different types of gearboxes need different methods of use, which is very important! No, a card friend got caught.
A truck family’s Liberation dump truck camyou, whose gearbox is the main gearbox non synchronizer type of fast. During off-road use two days ago, there was an accident that the gearbox suddenly burst and the vehicle could not continue to run without any signs. After communicating with camyou, he got some photos during disassembly and inspection.
The left intermediate shaft of the transmission has an impact after the intermediate shaft loses its positioning due to the broken left front intermediate shaft bearing, resulting in the open damage of the transmission housing. From the fracture trace of the transmission housing, there is no fatigue fracture trace, which can basically be determined as the instantaneous fracture after overload.
After opening the upper cover, it is found that the intermediate shaft gear inside the gearbox and the gear on the second shaft have teeth breaking to varying degrees, but this kind of Tooth Breaking does not belong to the form of normal spur gear tooth breaking, and the tooth tip is broken very irregularly, which is very similar to the impact of foreign matters.
While continuing to search carefully, it is found that there is a residual end of the shift fork at the bottom of the transmission. After understanding, the shift fork head of the shift fork of gear 5 / 6 of the transmission is the part with red circle in the figure; Asked the user if there was any noise or difficulty in shifting gears when driving, but the user said no; Then we rule out that improper gear engagement caused by bearing damage will affect the shift quality and lead to fatigue fracture of the shift fork.
Because the accident involved off-road dump trucks, combined with the use of some roads; Let’s simply assume that the gearbox is damaged, because the cardmate doesn’t often get on the bus, and the vehicle is often handed over to the driver. For the current operation of fast, each enterprise basically attaches importance to = 0. The user’s fast gearbox may adopt single lever left operation, which is not similar to the configuration with follow-up valve on the tractor, The high-low speed conversion of the transmission adopts the preselected valve type of left-right beat or up-down paddle of the shift handle.
Many drivers have great misunderstandings in the operation of this kind of gearbox, especially when they skip the grade and downshift to the low gear area in the high gear area, if the control is not good, Usually, when the torque is not completely interrupted, the main and auxiliary boxes shift at the same time (for example, directly jump from gear 8 to gear 6 or gear 5). At this time, the shift fork on the upper cover needs a certain thrust due to the sliding meshing sleeve itself and the gear speed to be changed. Under inappropriate circumstances, an alternating impact load is formed on the shift fork, which is easy to cause the fracture of the shift fork (after communicating with the user, it is learned that there are fish scale fracture trace areas in the broken stubble, which proves that fatigue has existed before.) a small shift fork has caused a loss of tens of thousands of yuan. Several simple actions have caused no small controversy.
As the saying goes, a good horse is matched with a good saddle. When we choose our favorite commercial vehicle to bring us wealth, we must make a reasonable planning and appropriate training for the use of vehicles, and never face all the use environment with empiricism.
For the type of gearbox without synchronizer in the main gearbox, let’s take 12jsd160 gearbox in this accident as an example. Because of its different operation modes, it is normal to change from 7th gear to 6th gear. When it is 7th gear, press the clutch to shift to neutral in the high-gear range, Tap the shift lever to the low-speed neutral (after the shift of the auxiliary box) and press the clutch to shift to the sixth gear in the low gear range. For the transmission with the follow-up valve and the preselection valve, the operation of the seventh gear to the sixth gear is to change the preselection valve from the high position to the low position in the seventh gear, press the clutch (after the shift of the auxiliary box) and press the clutch again to shift to the sixth gear. It is not to shift the paddle to the low gear after the seventh gear is taken out of neutral.
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