It should be a new unit and they should not have used a rebuilt differential. I would not have accepted that. I'm buying new so I want new. And it should have no impact at all on the warranty. As we just went through in a very long thread on here, there are not too many new motorhomes sold that don't have a list of items that need to be repaired. In my motorhome things I found within the first three days were: Generator overheated and shut down (Cause was a kinked cooling hose), wind sensor on the awning didn't work, turn signals didn't work, and then there was list of minor cosmetic items. Everything was eventually fixed by the dealer.