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How should the pre-selector valve for high and low gears on a truck be operated when switching gears?
Now truck engines are becoming more powerful, and there are more gears. The more gears a transmission has, the smaller the shift interval, making gear changes smoother and it is easier to find the most suitable gear, allowing the truck to perform at its best. However, multi-gear models also face more complex shifting operations.
▎▎Shift to neutral first then switch, or switch first then shift gear
▎Shift to neutral first then switch, or switch first then shift gear
Nowadays, whether it’s an 8-speed, 10-speed, 12-speed, or 16-speed truck, the gearbox shifting mechanism is generally designed with high and low gear ranges, and the number of gear positions is only half the number of gears (for example, in the picture above: 1st gear and 7th gear share the same position). For instance, an 8-speed truck only has 4 gear slots, a 12-speed truck only has 6 gear slots, and to engage all gears, a high-low preselector valve is needed.
The high-low range selector valve is very small in size and is generally located at the front of the gear lever. Our hand naturally rests on the gear lever, and the middle finger can reach it (and it is generally operated with the middle finger). On some models, the high-low range selector valve is positioned near the thumb and is operated by pressing. In fact, early models used a 'throwing shift' method to switch between high and low ranges. Usually, after shifting to the low-speed gear, the gear lever is pushed hard to the right to enter the high-speed gear, and then continue shifting. By comparison, the current selector valves are easier to operate and less prone to mistakes.
Regarding the operation of the selector valve, truck enthusiasts mainly use two methods: one is to return from the highest gear in the low-speed range to neutral, then lift the selector valve, and then shift into the first gear of the high-speed range. The other is to lift the selector valve directly from the highest gear in the low-speed range, then wait for 1-2 seconds, depress the clutch, and shift into the high-speed gear. Fellow truckers, which method do you use to operate the selector valve?
▎Official Explanation: Shift Up Without Returning to Neutral
Regarding these two shifting methods, truck drivers often say, 'Each has its own reasoning!' Everyone believes their own shifting method is correct, but in reality, the correct way is to flip the pre-selection valve from the highest gear in the low-speed range and wait 1-2 seconds before engaging the high gear.
Jiefang J7 User Manual
The Jiefang truck user manual also includes an introduction, clearly stating that the pre-selection valve should be operated first in the low-speed gear area, and then the gear should be engaged.
Fast Official Tutorial
Fast Official Tutorial
One of the components of the 'Golden Power Chain,' the Fast gearbox, also has an official operating manual, which points out that whether shifting from a higher to a lower gear or from a lower to a higher gear, it is necessary to first operate the pre-selection valve and then press the clutch to engage the gear.
Truck drivers must promptly correct their misunderstandings in driving. Although incorrect operation methods may not have an obvious impact on the truck in the short term, in the long term they will definitely reduce the lifespan of the gearbox and increase the failure rate of the gearbox operating mechanism. Therefore, drivers are encouraged to change their habits and adopt the correct gear-shifting methods.
▎Editor's Note
Developing good driving habits can ensure vehicle reliability for trucks, and for drivers, it means the vehicle is less likely to have problems, saving effort, trouble, and money. The operation of shifting between high and low gears is extremely simple, but changing habits is not easy. Therefore, drivers should make slight adjustments to their operational mistakes and develop correct driving habits.
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