I have to say I'm stumped. My EX35 started to make this metal grinding swinging noise every time I brake. It even does it for a few seconds after I stop and turn the car off. So it's not brakes or suspension. Mechanic confirmed it's not loose gas tank nor exhaust either and told me he can't see anything, saying it may be above the bottom parts and that it will require hours to get to the spot.
To me, it sounds like it's coming from the back middle, metal grind sounding like <eee> <aahh> <eee> <aahh> until it comes to a stop.

Any ideas what this can be?

The car has otherwise been a tank, regular maintenance, just over 100,000 miles (160,000 km).

The Suspect: 2008 Infiniti EX35 Journey with all options (360 Cam, lane departure warning, adaptive cruise etc).