I have a 2015 5085E and my tractor is doing the same thing at certain rpm's. I believe mine is around 16 or 1700 rpm. Below that speed gone above that speed gone. While it's making that noise, I can go around back and the hydro lines leading to the right side of SCV vibrate. It sends a horrible noise into the cab. I don't have my tractor right now, it's getting the dash cluster replaced, but when I get it back I'll try to get a better idea of what's going on and get back to you.