Why does a high-speed automatic transmission car experience gear disengagement?
4 Answers
If the gear drops during acceleration, it is normal. If the gear disengages during steady-speed driving, there might be an issue with the transmission. As the name suggests, an automatic transmission does not require the driver to manually shift gears; the vehicle automatically selects the appropriate gear based on driving speed and traffic conditions. Below are some reasons for gear disengagement: 1. Severe wear of transmission gears: The transmission mainly refers to the car's gearbox, which can be divided into manual and automatic transmissions. Gear disengagement is more likely to occur during gear disengagement driving. 2. Improper operation: The gear lever serves as one of the control operating systems in the car, controlling the speed and driving force of the entire vehicle. Sometimes, when the vehicle is driving on rough and bumpy roads, the gear lever may not be properly positioned, preventing the transmission gears from meshing correctly, leading to slippage and disengagement.
I often see cases of automatic transmission cars dropping gears at high speeds in repair shops, mostly due to stuck solenoids in the valve body or clogged oil passages. If automatic transmission fluid is not changed for a long time, sludge can form, blocking the oil passages and causing abnormal hydraulic pressure, which naturally makes it hard to hold the gear. Another easily overlooked issue is sensor failure. Abnormal signals from the gear position sensor can cause the computer to misjudge the vehicle speed, leading to an unexpected shift into neutral. Once, a car with 120,000 kilometers on it had this issue due to oxidized wiring harness connectors causing signal loss. If you encounter this situation, don't force it to drive. First, turn on the hazard lights and pull over, then tow it to a repair shop to read the fault codes for a proper diagnosis and solution.
Last month, my cousin's Lavida suddenly lost gear on the highway, which was really scary. It turned out to be a soldering point failure on the transmission control module—a common issue in older German cars. In my opinion, there are two scenarios to consider: if the gear slips during cold starts, it's likely due to insufficient oil pressure; if it happens after the car heats up, then clutch plate wear should be checked. Pay attention to gear shift jerks—if they become noticeably stronger than when the car was new, it's time to check the transmission fluid condition in advance. Remember, if you lose power suddenly at speeds over 80 km/h, keep the steering wheel steady and brake gently—don't make sudden turns.
If you notice gear slippage, first check the dashboard warning lights! Issues like hydraulic control unit pressure leaks or torque converter clutch slippage could be the cause. The trickiest case I've encountered was a Camry hybrid system failure where the drive motor got stuck in neutral. Regular maintenance can actually prevent 70% of such problems, especially adhering to transmission fluid change intervals – for example, ZF transmissions recommend fluid changes every 60,000 km. Here's a lesser-known fact: insufficient oil temperature in cold weather can also cause brief gear disengagement; letting the car warm up for three minutes before driving solves this.
