What Causes the Jerking Sensation When Starting an Automatic Transmission Car?
2 Answers
Automatic transmission cars may experience jerking sensations during startup due to the following reasons: 1. Internal clutch pressure leakage in the transmission. 2. Blockage or poor flow in the transmission oil circuit. This could be caused by wear in the oil circuit plate or long intervals between transmission oil changes, leading to reduced lubrication effectiveness. 3. Improper transmission oil level. Both insufficient and excessive transmission oil can cause jerking during startup. 4. Sludge buildup. The presence of sludge in the transmission oil can clog the oil passages in the valve body during circulation, resulting in jerking issues. Over time, this can lead to a series of transmission problems such as overheating, impact, and slipping.
I've been driving automatic transmission cars for over a decade and have encountered several instances of jerky starts. The most common cause is aged or insufficient transmission fluid, since automatic transmissions rely on hydraulic pressure - dirty fluid is like thickened blood that doesn't flow smoothly. Ignition system issues can also easily lead to jerking, such as worn spark plugs with insufficient ignition energy causing unstable engine output. There are also many transmission-specific problems, like dirty valve bodies clogging oil passages or worn clutch plates slipping. Another minor tip is that a dirty air filter affecting air intake can cause oxygen deficiency during starts, making RPMs fluctuate. I remember one time my car kept lurching at red light starts - inspection revealed worn engine mounts had lost their vibration damping, transmitting shakes directly to the cabin. Cold starts when transmission fluid hasn't warmed up tend to show more noticeable jerking. I recommend focusing on checking transmission fluid condition and engine performance - small issues left unattended become more expensive repairs later.
