What Causes the Clicking Noise When Starting an Automatic Transmission Car?
2 Answers
Automatic transmission cars produce a clicking noise when starting due to internal transmission issues and excessively low engine RPM. Internal Transmission Issues: Excessive wear creates gaps, leading to play during startup, which results in the clicking noise. Excessively Low Engine RPM: Insufficient output torque may cause gear dragging, potentially resulting in abnormal sounds. During rapid acceleration, when engine RPM rises extremely quickly, the transmission may experience a shock during the shift from 1st to 2nd gear. When heavily pressing the throttle to raise RPM to 5,000-6,000 or higher, the transmission must abruptly reduce RPM from 5,000-6,000 to 2,000-3,000 during gear shifts to stabilize engine speed, creating this impact. Maintenance Methods: Replace transmission fluid and perform comprehensive transmission maintenance. Additionally, avoid aggressive driving to prevent accelerated transmission wear. Another important note: regardless of gear shifting operation, always use the foot brake to completely stop the vehicle first.
I often tinker with my car, and encountering a clunking noise when starting in automatic mode is quite common. Most of the time, it's due to wear on the drive shaft universal joint, which is responsible for transmitting power. Over time, the gap increases, causing a clunking sound when accelerating. Brake pad sticking is another reason, especially after humid weather. If the car is parked overnight, the pads can stick to the rotor, resulting in a noise when releasing the brakes. Another possibility is aging or loosening engine mounts—if the rubber blocks are worn, they can wobble. Insufficient transmission fluid can also cause a jerky feeling when shifting gears and starting. I recommend not delaying and checking the drive shaft and brake system promptly. Otherwise, it could worsen into serious issues like a broken axle or brake failure. Regular cleaning of brake pads and topping up fluids can prevent this, and it's best to start smoothly without sudden acceleration.
