C300de engine OM654 with 50k km.

I'm trying to find what is this metallic rattle coming from underneath the car, If I hold the revs just above idle it disappears, If I lightly blip the throttle it makes a rattling noise as the revs go down back to idle. It reminds me of a rattlesnake shaking her tail for a second for every throttle blip.
I had an old cheap car that made this rattling noise but never found out what it was nor I could find anything on the internet that had the same noise.

Since this is a completely different beast in every aspect in this case I suspect it has to be something related to the transmission, perhaps the DMF because when I switch to D the noise disappears. Only happens in Neutral or Park.

 

Many undercarriage parts are qualifed to double as musicians...
-- the heat shields near exhaust lines
-- the belly pans can be missing a number of screws
-- the tranny mount can be bottom out
engine compartment has exhaust shields

> You're gonna need to narrow this down physically
🤞

 

I will be doing an oil change this weekend, will try to narrow it down and post an update.
I've tried recording but my phone has an awful background noise cancellation so it's very hard to hear it on video.