Originally Posted by calclimber
Mine also makes a flapping noise, I think it may be the propane,waterfill door on the drivers side flapping in the breeze. :roll:
Craig 2005 eb 50 PH 4x4 V10
Interesting thought. Mine doesn't make a flapping noise, but I have no propane. Why not duct tape the fill doors and try to replicate? That's how I found out that the large incut inside for the water drain (behind the fill line) shoves TONS of air into the van over about 60 mph; duct taping over that stopped it.
Come to think of it, maybe that's it. I'm talking about the big rectangular hole cut on the inside of the outer van wall, where the drain line for the water fill is. When I'd hit 60+ MPH, I'd get a strong breeze coming into the cabin (and could hear the road) right behind me. Turns out SMB screwed up some dimensions on my interior, so the plastic shroud that covers where the seat belt is doesn't stay attached. Thus, that became the path of least resistance, and it was like having a vent on full blast, made up of air from the outside, when I'd hit about 60 mph. If you have the same issue, then perhaps the air being forced into your van interior is finding a _different_ path of least resistance, is moving up through your interior wall to a higher point, and perhaps that's causing some of the insulation edges to flap!
Regardless, I tested out and confirmed that this was the source of my air infiltration by covering the entire hole with duct tape, then hitting speed again.... no air blowing inside from the outside! This might be your issue.... Try it, and report back...