Hello folks, I have a 1989 u280 with the bottom of the coach coming down some on the battery and fresh water tank floor. Thought someone may have done a repair at some time. I have owned the RV sinse 2016 haven't needed any parts from the dealer. lol well I called Nacogdoches ask the lady if I could speak to the forman, or parts,lol well was told that I have to be a member to talk or buy hummmm so may have to become a member, mainly needed to know what the under floor looked like before going into it well thanks and travel safe.
Jimmy on these forms it's always best to put a picture of what it is you're talking about so that we can get a visual idea. But from what it sounds like you have maybe some corrosion up underneath there and that could be a really bad thing. As far as getting advice from for travel yeah you need to be a motorcade member for them to do that these days.
Sounds like the rear bulkhead is bad.
Read up on bulkheads.
Post pictures of both rear bulkhead and battery area.