What Causes Jerking When Starting in D Gear with an Automatic Transmission?
2 Answers
Automatic transmission jerking when starting in D gear is caused by: 1. Internal contamination: Persistent dirt and impurities inside, especially when they accumulate in the valve body and form blockages, preventing effective regulation of oil pressure, leading to jerking, impact, and slippage issues. 2. Excessive vehicle temperature: High temperatures can degrade the quality and friction characteristics of automatic transmission fluid, increasing friction and wear, resulting in transmission noise. Additionally, sludge (impurities or dirt) can form inside the transmission (e.g., in the valve body), causing jerking and impact. If the temperature exceeds 120°C, rubber sealing materials begin to harden, eventually leading to leaks and reduced hydraulic pressure. At even higher temperatures, the transmission may start to slip, which in turn further raises the temperature.
Having driven for over a decade, I've noticed that jerky starts when shifting into D gear in automatic transmissions are quite common. Dirty or low transmission fluid is the most frequent cause—over time, the fluid thickens and hampers the smooth operation of the valve body. Next is clutch plate wear or slipping, especially in older cars or after aggressive driving, where severe wear can disrupt power delivery. Sensor failures, like faulty speed sensors, can also cause the transmission control module to miscalculate. When driving, avoid stomping on the accelerator during starts and allow more warm-up time in cold conditions. For maintenance, change the transmission fluid every 40,000–50,000 km using the manufacturer-recommended fluid. While jerky shifts may seem minor, neglecting them could lead to costly transmission overhauls—penny-wise but pound-foolish.
