What Causes Shaking When Braking in D Gear?
4 Answers
If the shaking when braking in D gear is slight, it is a normal phenomenon. However, if the shaking is severe, it may be caused by damage to the engine mounts. The engine mounts, usually made of rubber, are located where the engine connects to the frame and serve to cushion the engine's vibrations. D gear, also known as the drive gear, engages the corresponding forward gear hydraulic circuit automatically based on throttle opening and vehicle speed signals when the gear selector is in this position. Automatic transmission cars use an automatic transmission to adjust speed, where the transmission's control system automatically selects the appropriate gear based on engine speed and load, replacing the driver's subjective judgment and manual gear shifting.
When your car shakes while in D gear with the brake pressed, I often hear owners complain about this issue. The main reason is unstable engine idling—when the engine speed is too low or unstable at idle, the transmitted force causes the car to vibrate. Specifically, it could be due to old spark plugs. After years of use, the ignition efficiency of spark plugs declines, leading to fluctuating engine power. Another possibility is a clogged mass airflow sensor, located on the intake tract—dirt buildup can disrupt air supply, causing the engine to shake. Additionally, worn engine mounts can also lead to this phenomenon. Mounts act as buffers; when they age, they can no longer absorb vibrations effectively. I recommend checking these areas first—don’t let minor issues escalate, as they can affect driving smoothness and even increase fuel consumption. Regular maintenance, such as replacing spark plugs and cleaning the intake system periodically, can help prevent shaking problems.
As a veteran driver with over a decade of experience, I've personally encountered this issue: stopping at a red light in D gear with the brake pedal pressed, feeling the car body shaking incessantly, which is quite annoying. The main suspected causes are: engine RPM fluctuations at idle when the engine is stationary, unstable RPM can occur if there's too much internal carbon buildup, such as a dirty throttle body or inefficient spark plugs; the braking system is also to blame—if the brake discs are worn unevenly or the calipers are loose, it can cause shaking when opposing the engine's power; another common issue is with the automatic transmission's torque converter, which might slip at low speeds. My advice is to address it early once it happens—first, take it to a repair shop for a mechanic's diagnosis, as checking the engine and transmission is usually straightforward. Don't underestimate this shaking; prolonged exposure can cause significant engine wear and even affect driving safety. Develop a habit of regular maintenance to minimize such troubles.
This shaking is mostly due to power issues when the engine is idling. In automatic transmission vehicles, the engine continues to operate when stopped, and unstable idling causes vibrations. Specifically, it could be caused by old or damaged spark plugs leading to power fluctuations due to improper ignition; or damaged engine mounts, which are designed to reduce vibration transmission but fail when worn out; or carbon buildup inside the engine affecting the air-fuel ratio. It's not difficult to fix—try a simple inspection or replacement of the spark plugs. Delaying repairs may worsen the wear.
