What are the reasons for jerky shifting when changing gears in place with a CVT transmission?
4 Answers
The causes of jerky shifting when changing gears in place with a CVT transmission are as follows: 1. Damage to the valve body and solenoid valves: If the valve passages are blocked or worn due to contaminants in the transmission fluid, it can affect the pressure supplied by the valve body to the clutches, leading to insufficient or uneven pressure and causing the driver to experience jerky shifting. 2. Burnt steel plates and friction plates: Burnt clutch plates not only cause jerky shifting but also result in poor driving performance. The debris from the worn friction plates can further contaminate the transmission fluid. 3. Irregular transmission fluid changes: If the automatic transmission is not maintained for a long time, various performance indicators of the transmission fluid, such as lubrication, viscosity, and temperature stability, will significantly decline. Particularly, the temperature of the automatic transmission fluid can rise excessively if the radiator is dirty and unable to dissipate heat. When the computer detects high temperatures, it may enter an emergency operation mode, forcing upshifts (locking into a specific gear). This can lead to symptoms such as the vehicle not accelerating properly, experiencing dragging sensations, and jerky shifting. When the fluid temperature exceeds 135°, it can cause significant damage to components like friction plates and clutch plates.
I'm all too familiar with the jerky gear shifts when stationary in a CVT car. The main culprit is usually overdue transmission fluid changes—when sludge builds up in the oil pan, the fluid pressure becomes unstable, especially during cold starts when gear shifts feel particularly harsh. Sticking solenoids or worn seals in the valve body are also common issues; if these fail, sudden pressure changes during gear shifts cause that noticeable 'clunk.' Another possibility is worn engine mounts transferring vibrations into the cabin, making you mistakenly blame the transmission. My usual advice: first check fluid level and quality, then scan for trouble codes. In most cases, replacing the valve body solves it.
Last time, my best friend's CVT car also had this issue—it would jerk and shake when shifting gears while parked. After inspection, it was found that the steel belt was severely worn. When slipping occurred, the transmission computer would desperately adjust the oil pressure to compensate, resulting in even harsher gear shifts. This is also related to driving habits, as frequent hard acceleration and flooring the throttle can particularly damage the steel belt. Additionally, the transmission computer program can sometimes act up, causing erratic shift timing. It’s best not to delay—take it to a professional shop early to connect to the diagnostic computer and check the data stream. See if there’s an issue with the oil pressure sensor or speed signal to avoid turning a minor problem into a major repair.
CVT gear shift hesitation while stationary is basically caused by three reasons. First, the transmission oil oxidizes and deteriorates, leading to insufficient lubrication and oil pressure fluctuations. Second, the precision valves inside the valve body wear out, causing inaccurate oil flow control. Third, the gap in the steel belt and cone pulley set increases, resulting in inconsistent power transmission. This is most noticeable during cold starts because the oil temperature hasn't risen and its fluidity is poor. Regularly changing the original oil is crucial. When driving, avoid keeping the brake half-pressed in D gear for extended periods to reduce the load on the steel belt. If accompanied by a buzzing noise, it's likely the bearing is worn out and needs to be replaced as a whole set.
