What is the reason for the failure to switch between high and low speeds?
3 Answers
Possible reasons include staying in neutral for too short a time, which is the most common cause; another possibility is gear clash in the auxiliary box. Here are some additional details: 1. Inspection: If there is no high-gear start and the operation is correct, then thoroughly inspect the air pressure, air pipe, pre-selector valve, shift cylinder, auxiliary box shift fork, auxiliary box synchronizer, and auxiliary box drive gear. If no other issues are found, these can be disregarded. First, consider the shift cylinder and fuel tank synchronizer. 2. Precautions: It is recommended to switch between high and low gears only between 4th and 5th gears. Skipping gears when switching can cause severe wear on the auxiliary box synchronizer, leading to malfunctions. When parking, only park the vehicle in neutral in the low-gear range, meaning the shift lever's side knob should face downward. It is strictly prohibited to park and shut off the engine in neutral in the high-gear range, as this may cause serious malfunctions.
The issue of gearbox shifting between high and low speeds is something I've dealt with countless times in my career. Common causes include insufficient hydraulic system oil pressure or deteriorated fluid leading to sluggish gear changes. Faulty sensors like the vehicle speed sensor providing unstable signals can prevent the ECU from accurately determining shift timing. Other factors such as stuck solenoid valves or mechanical wear like clutch plate slippage also affect shifting. Symptoms include slow response during acceleration and strong jerking sensations. I recommend promptly checking fluid quality and level – replacing transmission fluid in older vehicles often yields significant improvement. Neglecting such faults accelerates transmission damage, potentially doubling repair costs later while compromising overall driving experience and vehicle lifespan.
After driving for decades, what frustrates me the most is when the transmission gets stuck in low gear and can't shift up to high speed. This is often caused by dirty or insufficient transmission fluid, leading to inadequate pressure for gear changes. Issues with electronic components like a faulty speed sensor sending no signal, or loose wiring connections causing poor contact, can also be to blame. For self-diagnosis, if you notice the tachometer climbing when you press the accelerator but the vehicle speed doesn't increase, that's a telltale sign. It's crucial to visit a professional shop for a diagnostic scan immediately. Don't make the same mistake I did last time by delaying—it ended up requiring a complete transmission teardown and overhaul, wasting time, effort, and money. Addressing the issue promptly can prevent the risk of breaking down on the road and ensure driving safety.
