This is a hard one to describe. My van (2010 E-230 6.0L Diesel) is running great, no Check Engine light or codes on the Edge CTS however I hear a weird rattling/grinding/scraping noise. It almost sounds like a small motor has kicked on that rarely gets used. I tend to hear it after finishing a medium or long uphill where I've been running at 2500+ RPM and then finish the hill and let off a bit and back down to 1500 RPM. At the point I let off some, but not completely is when I hear the noise.
Here is a link to a video I took to try and help:
It's an iPhone video so the audio isn't great. The first part of the video features the weird noise, then it goes away in the second part of hitting the gas again and stays gone until the end when I let off the gas completely.