Thanks for the response.
Forgot to say that it's a 2006 SunSeeker 3100SS Ford. We bought it in November 2015; it's our first motor home.
Hadn't thought about the stove, but it could be. Other Half said the stove rattled something awful driving back from the dealer. Have to check that on our next trip.
I doubt it's the drive shaft. My Maverick (still miss that car!) got towed in San Francisco and the clowns misaligned the rear U-joint. The car felt like it was shaking itself to pieces above 25mph. This did not feel like that.
As I said, I noticed the noise at highway speeds, around 50-60mph. Did not notice any other symptoms. No shaking, or anything else, so it sounds like the stove may be culprit. I think we had an egg timer sitting on the stove, but am not sure.
This was on the way back from "drydock" (Camping World had just worked on one of the tire-pressure monitors).
2006 Sunseeker 3100SS - "Heart Of Gold"