Why does the car sometimes make a 'thud' sound when braking?

[OLilliana]

Unusual sounds when braking could be due to normal ABS operation, safety reminders, loose chassis components, or unstable brake discs. The details are as follows: 1. ABS working process: It is actually a cyclic process of locking-releasing-locking-releasing, keeping the vehicle in a state of near-lock rolling. When you brake hard and trigger the ABS, it will produce a 'clunking' sound, which is normal. In this case, just press the brake pedal firmly to the end. 2. Safety reminder: If you hear a 'thud' sound between the transmission and the gear lever when pressing the brake pedal, the main reason for the sound may be the electronic linkage between the brake system and the automatic transmission. Pressing the brake activates the transmission solenoid valve, which produces a 'thud' sound. At this time, you need to press the gear lever lock button to shift gears, which serves as a kind of safety reminder.