What Are These Holes For?

jmiller0526 · February 10, 2009

So i am slowly piecing together a stereo for my Ext Cab Sierra (2008) and because most of the stuff will be here soon i thought it would be a good day to start tearing the truck apart and applying some deadener....

I took out the back bench and moved all of the stock deadener stuff out of the way and i found this plastic peice

which was in this hole

it is the weirdest thing i have ever seen, and i cannot for the life of me figure out what their purpose is. There is one on each side of the cab and if you look between your bed you can see the outlets of them.

i decided i would rather not have 2 large openings in my cab so i spent about 4 minutes cutting apart an old table that was in the garage and putting them on the outside for the time being. These are temporary until i can figure out a better solution or figure out what they do.

i am glad i found them though regardless of what they are for because it will make running reverse camera wire and a Ham radio antenna much easier.

So if anyone knows what these things are for i would love to know

asilverblazer · February 10, 2009

Vents, you should see them flap open when you close the door.

dayday · February 10, 2009

I "think" they allow the cab to vent when you open/close the the doors....?

jmiller0526 · February 10, 2009

should i not seal them off then?. i dont understand why they would put a vent behind a seat back and 1/2" of foam padding...i believe you i just dont understand why

VMax2007 · February 10, 2009

should i not seal them off then?. i dont understand why they would put a vent behind a seat back and 1/2" of foam padding...i believe you i just dont understand why

Same reason they tell you to crack your windows for a few days after getting your windshield replaced so you don't pop it's seal before it fully cures.

solarjustin · February 10, 2009

Vents, you should see them flap open when you close the door.

When you slam your door you cause a very big pressure spike and the vents give that pressure a place to go. The back of the cabwall has been the place for these vents for many years.

Zembonez · February 10, 2009

should i not seal them off then?. i dont understand why they would put a vent behind a seat back and 1/2" of foam padding...i believe you i just dont understand why

Definitely do not seal them. When you have the AC or heat on, they allow air to go somewhere. Otherwise, it would just pressurize the cabin until it didn't blow any more. Those vents are critical to the HVAC system.

JoshRDavis.84 · February 10, 2009

Another vote for not sealing the vents

jrrod2004 · February 10, 2009

seal em and let us know how quiet your truck becomes

tobias · February 10, 2009

I say make new vents out of bacon so every time you get in your truck it smells good.

DenaliJay · February 10, 2009

should i not seal them off then?. i dont understand why they would put a vent behind a seat back and 1/2" of foam padding...i believe you i just dont understand why

If you seal them off, you will have problems with air flow in the cab, such as, when you go to close the door, there will be pressure built up in the cab. The door might now close all the way.

Outbacker · February 10, 2009

If you seal them up, and slap a door closed there is a chance that you can damage the window seals due the pressure built up inside the cab. I had asked this question on my last Sierra, and that was one of the reasons the vents are there. Good question though.