I finally got around to getting those "missing" flapper seals installed under the front cowling. I recommend it. I have smelled absolutely NO fumes at idle when on vent since I had them installed. Before installation I smelled it every time I stopped, and had to switch vents off, or go to recycle. Maybe other trucks need even more sealing off, but I sure recommend people try it if you've had the fume problem in your cab! ( I had it installed at "the" dealer, and no scratches on truck. When I picked it up I said to the service manager "I've heard quite a few of the trucks have had them missing." She says-" Well- they're not really missing, they just didn't put them on."

 

exactly where are they located... What is the front cowling????

 

Check out this thred I already uploaded picyures of the fix:

https://www.dieseltruckresource.com/...5&pagenumber=1

 

Thanks ttreibel!

 

A down-loadable copy of Dan Rounsevell's fix can be found here:
www.rounsevell.com/blowby.pdf

The part # to get for the lower openings is 55276332AB for a quantity of 2.