I was just wondering if anyone else is picking up a whine around the sweet spot of 50-60 mph, sounds as if its coming from either the Transmission or Differential. The sound is not apparent below 50 or above 60 mph but just where you don't want it... Only have 2,500 miles on the MH, so it might still be bedding in and fade eventually or get get worse, knowing my luck the latter.
Nope. No whining noticed. And, I'm on my third F53, (Fleetwood, Winnebago, and now a Thor), since 2004.
My 2004 Fleetwood Pace Arrow did blow the original transmission at around 1800 miles, but that sounded more like a toaster was being shredded by a Blendtec blender at 65mph, a tiny bit louder than a whine.
No whinning here either but check out your front wheel bearings. Posts here have stated the nuts are torqued too tight which causes the bearing to overheat and weld themselves to the axels! I checked mine and they were fine - but I did not have any strange noises.
Just one thing to check for. Easy check is to feel the wheel after a highway drive if they are scalding hot.
We had an annoying high pitch whine or whistle in our Daybreak. Like yours, it only happened above 55 mph. It was wind noise caused by the front grate. I removed the grate and problem was solved. BTW, Ford V-10's are notoriously noisy.