Rear cab pressure seal?

[Zstreet86]

So today when closing my passenger rear door, I was standing in such a way where I could see the space between the bed box and the cab. When I closed the doo, I noticed out of the corner of my eye, a flap move in that space well below the glass. It seemed like it was relieving pressure/air from the cab? Anyone else notice this or know how it works? Maybe this could be the source of the leak I've seen some people post about if it doesn't close/seal properly.

 

[Pressgrove]

Not sure about that, but some believe that is why the rear doors sound cheap when they close (the noise is from the flap, not the door).

 

[Chaser]

Caught mine doing the exact same thing today. Any others notice this? Is this supposed to happen or is something loose?

Mine only really does it on rear passenger side.

 

[Cummins359]

Yes, its supposed to happen. Ots letting the pressure out. Open your windows and they won't move.

 

[Biga]

Most cars and trucks have a pressure vent, if not the windows could blow out when you close a door. Trucks have them at the back of the cab, most cars have them in the trunk behind the bumper.