Though most people seem to believe that car doors require a resounding push, slam, and bang, the reality is that all you need to do is close the door gently for an active latch. That is the way doors are built. The problem is the slam-bang mentality.
How modern car door locks work
Today’s car door lock has two parts, the locking mechanism and the door strike.
When the lock opens, a plunger-style rod is activated and presses a switch downward that opens the jaws of the lock. The opened jaws release the striker and the door swings open. The jaws remain open until the door closes again.
On closing, notches at the base of the door lock jaws react to the impact of the strike, closing the jaws of the lock.
To work correctly, the door lock mechanism and the strike must line up exactly. If a door is repeatedly slammed, over time, the lock and strike can become misaligned. The door lock can then “float” within the strike and rattle.
It’s better to close a car door gently as slamming it will result in rattling noises in the door. Also, many of the door locking mechanisms moving indoor parts are made of plastic. The plastic parts can easily also become misaligned and can contribute to door rattles.