Vibration, Resonating Noise

[pcm1959]

Kind of long post but trying to give as much info as possible to get good advice.
I'm the 2nd owner of a 2015 Winnebago Vista 27n on a Ford 2014 18k chassis. I purchased it a thousand miles from home back in July with less than 7k miles. The drive home was good other than a reverberating noise that I thought was wind turbulence produced by the mirrors deflecting air against the side windows, aged out tires out of balance out of round, etc.
The coach had the original tires on it, too, so I tried not to be to critical until I got it home and had new tires installed as well as an alignment.
Well that's all done now and I still have the obnoxious reverberation.
Yes, its like someone pounding on a glass window. It comes on goes at times but overall is pretty constant above 50 mph.
Today is only our third trip with the coach. The first two were only 1 hour drives in which 30 minutes were highway. Today was a 4 hour trip mostly highway. So today I walked around inside the coach while the other half was driving. I do NOT think the issue is what I originally thought!
We don't experience vibration at our feet in the cab area or in the steering wheel. Nor do I notice the vibration in the rear even standing right over the rear axle.
I first noticed our cat shaking while riding on the sofa which prompted to get up. Right when I got about 5 feet behind the cab area is when I felt the vibration shaking the sofa and even the sink cabinet across from the sofa.
So again, I walked to the rear of the coach and stood right over the rear axle and no vibration. It's strictly in the middle.
So once parked, I looked underneath and I can see a drive shaft joint and frame mount right in the vicinity of where I felt the vibration.
Does this sound like anything anyone else has experienced? Could I have a drive shaft issue?
It's really obnoxious and makes an otherwise nice drive a bit annoying.
Thanks in advance.

[Gjac]

If you cat was bouncing up and down I would check the tires for out of roundness.

[Bikeboy57]

If you have a smartphone there are several vibration analysis apps available. Mine will give you frequency. If you know driveshaft rpms, tire diameters, and other rotating part info at a given speed, then the math is simple to figure out what is the likely culprit . The phone can help you find the he location by moving it around and measuring the amplitude.

[DSDP_Don]

Good job of locating the vibration. You have a two piece driveshaft with a carrier bearing in the center....the joint you're seeing. Before throwing parts at it, I would find a true driveshaft shop and let them check it out. The coach is fairly new, but who knows if the original owner might have struck something.

[CA_Traveler]

Kitty found it! Replace the mount rubber etc and have the drive shaft rebalanced which includes U joints issues.