Stange Knock knock sound when in D and R gears
My Merc C class CDI 2006 makes a strange noise when I put the gear to D or R (it's like a knock). When I put the gear to P and N, the noise fades away. When I drive the car fast it makes less noise. I can hear the noise coming from the engine part, but I am not sure. I have attached a video to this post. Does anything know if this has to do with the auto transmission? Some engine part? Or maybe the injectors? Please let me know. Thanks a lot.


