What is the reason for a clunking sound when braking in reverse?
2 Answers
The reason for a clunking sound when braking in reverse is the electronic interaction between the braking system and the automatic transmission. When the brake is pressed, the transmission solenoid valve opens, producing the clunking sound. At this point, the gearshift lock button must be pressed to engage the gear. The function of the brake is to reduce speed or bring the vehicle to a stop. Its working principle involves converting the kinetic energy of the moving vehicle into heat energy through friction between the brake pads and brake drum, as well as between the tires and the ground, thereby slowing or stopping the vehicle. Causes of brake failure include: 1. Impurities or poor sealing in the brake master cylinder; 2. Failure of the vacuum booster pump; 3. Contaminated brake fluid; 4. Leakage in the brake master cylinder or wheel cylinder; 5. Air leakage in the air reservoir or pipeline connections; 6. Severe overloading; 7. Carbonization of the brake drum; 8. Insufficient brake fluid in the master cylinder; 9. Wear of the master cylinder piston.
I've been driving for over a decade, and the clunking sound when reversing and braking is extremely common. There are mainly three reasons: First, when starting a cold car, the brake pads and rotors stick together, especially after washing the car or on rainy days. When you reverse, the sudden release of resistance causes a 'click' sound. Second, aging chassis components, such as cracked control arm bushings or worn stabilizer bar links, produce metal collision noises when the force direction changes during reversing. Third, excessive drive shaft play, most noticeable in rear-wheel-drive vehicles, causes a jolt when the power engages during reversing. It's important to assess the situation—occasional sounds are nothing to worry about, but if every reverse is accompanied by body shaking, you should immediately check the chassis.
