Reasons for a Thud Sound When Accelerating from a Start in an Automatic Transmission
3 Answers
Reasons for a thud sound when accelerating from a start in an automatic transmission: 1. Transmission issues, including loose drive shaft, transmission wear, worn output shaft inside the transmission, or worn transmission gears. 2. Gear shift position malfunction. Tips for starting an automatic transmission car: 1. Without pressing the foot brake, press the start button twice to initiate the car's computer system self-check, lasting at least 6 seconds. 2. Press the foot brake and press the start-stop button to ignite. 3. Release the foot brake and warm up the car in place. 4. Press the foot brake, release the handbrake, and shift the gear from P to D (if starting on a slope, to prevent rolling back, first shift to D, lightly press the accelerator, slowly release the handbrake, then start smoothly). 5. Gradually release the foot brake to start. 6. Depending on road conditions, steadily press the accelerator to speed up and drive safely.
I've been driving an automatic transmission car for over ten years and often encounter a clunking sound when accelerating from a stop. This noise has caught my attention because if left unaddressed, it can lead to major issues. The most common causes are loose or worn-out CV joints in the drive shaft or half-shaft, which create unstable power transmission and produce noise when accelerating. Another possible reason is aging engine mounts, where cracked rubber components cause the engine to shake and collide during startup, resulting in noise. Additionally, damaged transmission bushings can create similar sounds. My advice is to promptly visit a repair shop for an inspection—minor issues like replacing mounts can be fixed quickly. Delaying repairs may lead to damage to larger components, compromising driving safety, which is not worth the risk. Remember, unusual noises during startup are often signals of mechanical failure—don't ignore them.
I often enjoy tinkering with my car's maintenance in my spare time. That clunking sound when starting an automatic transmission is mainly a powertrain issue, such as a loose half-shaft or aging transmission mounts. From a basic maintenance perspective, first park the car and check for obvious cracks in the engine mounts underneath, or inspect whether the driveshaft joints are loose. If you're not very knowledgeable, you can lightly press the accelerator a few times to test and confirm the frequency of the abnormal noise. Regular maintenance is key—ignoring these small issues may lead to severe wear and skyrocketing repair costs. My experience is: pay attention to unusual car noises early, address them promptly, and avoid costly major repairs later.
