Draft at back of cab?

[jonny24]

So, I was leaving work today, and had the windows open as I was pulling out to let the hot air out as the AC was getting up to speed. When I shut the windows I heard what was almost like a rattle coming from behind the seat, but not quite, and nothing else was rattling (smooth road).

 

I reached behind the seat, and it was my plastic bag that holds my detailing cloths. But it was't rattling, it was fluttering from a "breeze". It was coming from the back of the cab. There's the plastic piece that's below the window, with the popouts for child seat anchors that goes a third of the way down, and below that is a kinda loose carpet panel that goes another third of the way down, and this draft was coming from (or going to?) up behind that right in the middle. It was pretty steady, and went away when I shut the fan all the way off.

 

Anyone know what this is? Air return for the HVAC? I would have thought that was under the dash somewhere.

[fondupot]

Those are the cab vents. Those are there so the air can move in/out as you open the doors. If the cab was perfectly sealed, it would be a lot harder to open the doors.

[jonny24]

Those are the cab vents. Those are there so the air can move in/out as you open the doors. If the cab was perfectly sealed, it would be a lot harder to open the doors.

 

So are they connected to anything? Or do they just go outside? I'm at work so I can't check right now, I'll investigate tonight.

[fondupot]

They just vent to the outside. They are little flaps that open with air pressure to vent the cab. Pretty much all modern cars and trucks have these.

[6.2 Sierra]

I had a 2011 Sierra crew cab. The road noise was pretty loud. A friend of mine worked in the service department for GMC. I mentioned it to him and he said they have some sort of dampening material they can put where those vents are you're talking about and it would help quiet the noise a little. So I dropped my truck off and the dealership installed the material under warranty and it helped the road noise tremendously. Doors still opened and closed fine. The material didn't close the vents off.

 

 

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[jonny24]

Interesting... I don't notice any noise back there, if it weren't for the plastic fluttering I never would have known they were there.

[thefishhawk]

there is already soundproofing over the vent, and if you have the auto rear window there are cables coming through it right next to the vent. if you get under the truck and look up between the cab and bed you can see it. might even be able to get a hand up there. it's actually a pretty big vent, maybe 3x6".