I know this is a trivial problem compared with gas mileage, DPF cracks, etc. But my 2008 F350 XLT crew cab 6.4L has a high pitched whistling air-leak sound when I turn the air conditioning on. It goes away if I put the AC on recirc. It seems to be coming from the rear passenger door, perhaps the door handle. Or is there a vent behind the rear seat?

Anyone else have this problem (and is there a quick fix)? The dealer will handle it I am sure, but I don't want them laughing at me - especially after they just had to pull my tranny to replace a small leak at a gasket between two housing sections.

 

Answered my own question. Behind the crew cab back seat are two vents with rubber flappers on them. They are covered by the carpeting on the back wall with thick insulation, but there are cutouts in the carpeting just below the vents. I had crammed so much stuff back there, that I covered up the carpeting cutouts, and there was no way for the air to get out of the cab when recirc wasn't on except through a door gasket.

 

Darn, if I'd have seen this thread this would have been a question I could have answered and saved you three months wind whistle in the process.

Glad it was nothing serious.