I have a 2017 E350 (6.8L) chassis RV . When accelerating around 40 to 42 mph and 60 to 63 mph I hear a scratching sound (sounds like static or sandpaper on wood or metal). Doesn’t happen all the time, but more often than not. Doesn't happen when cruising. Seems not to affect performance, Ford service couldn't find anything wrong. This is a 2-wheel drive, not a 4-wheel drive. Any help solving this mystery greatly appreciated.

 

Open the window and let the 🐈 in- probably hangin' on for dear life. LOL

All joking aside, I'd start by figuring out if the noise is occurring at a consistent RPM and then try to duplicate sound while revving engine in park. Perhaps there is a loose part somewhere that causes the sound. If it doesn't happen in park then you can focus on components that are in play while in motion. Could be something in brake rotors like a pebble stuck in pads causing it to rub in oscillation . I actually had this happen before. Sounded like light scraping noise and eventually turned to light squeal only at certain speeds. Good luck!

 

I'll give it a try. Thanks

 

The noise consistently started at 2000 rpm. Brought it in for service again. It was a deformed serpentine belt. Replaced it and noise gone. Simple as that. Thanks