Truck Cab Rear Pressure Vent *Research Experiment

I discovered a large vent in the rear of the cab this weekend when I pulled apart the rear seats in my 07 access cab. I didnt think anything of it until I drove down the streat with the seats off. The vent kept popping open which resulted in road and wind noise. I know now that this vent is what I have been very annoyed by ever since I got my truck. Several times I had my wife searching the side and rear windows for leaks.

Yesterday I decieded to see what would happen if I taped it up so that I could reduce the road and wind noise. I applied a light layer of masking tape to the top of it. I made sure that there were no gaps and that it stuck to all sides.

I know what you are thinking, I kinda thought the same. This vent eliviates pressure in the cab especially when closing the doors or when the AC/heat is on. The air needs to go somewhere right. I was event told that if you plug up the vent then your ears will explode when you shut the door because of the pressure. Well it was my thinking that there are enough holes and gaps throughout the cab to account for this without having a large vent.Besides it seamed like my vent was defective because it just opened up randomly when driving down the street.

Results - Test 1
I did not notice a difference when shutting the door, opening the window or turning on the heat. The windows didn't fog up (and it was a cold one this morning). The fans were not struggling to push air (was not on recirculate). My ears did not explode.

What I did notice is highly reduced road and wind noise.

At first impression I am very pleased with the plugged up version. I will continue to test this out as I have a couple more days to install new speakers and Raammat sound deadener. I will add a couple layers of tape and make sure it is fully sealed.
I might do a second test of just pushing some porus foam down in the vents to still allow air to flow but reduce the velocity and the noise.

I hope that this test helps out someone that is annoyed by the wind and road noise or sparks some discussion.









Results - Test 2
I taped up the vent with double the amount that was already on it. I made sure that there were no gaps at all. This time I did experience a pressured cab. The AC/Heat fan speed was reduced by almost half. The second I turned on the AC/Heat I could feel the pressure in my ears. Shutting the door still was no problem though. The windows did not fog up either. I did not test the windows being open to see how much inflow there was but I will try to do that on my way home from work today.

In general the road noise was reduced in half and the the wind noise was almost eliminated after plugging up the vent. From the vent there was no noise at all.

Next test will be to push some foam down in the vent. My thought on this would be that it will reduce the noise but still allow some flow of air. If this holds true then the AC/Heat should run full speed.
I am also considering a way to hold the rubber flap down unless there is higher pressure in the cab. As I mentioned before with the AC/Heat off and windows closed the flap opened up randomly down the street and stayed upen for most of the time. The pressure in the cab should not have been changing much at all. Actually when I felt the vent when this occured it almost seemed like the air was being driven into the cab, not out of the cab. I was thinking about a rubber band or a some double sided tape. Any other ideas?



Results - Test 3
I inserted some foam pieces into the vent. The foam eliviated the higher pressure in the cab. The AC/Heat felt the same as when I opened the window, no flow restriction. The road/wind noise increased however. I could hear times when driving down the road that the vent would open up. It was muffled from the standard but still not perfect. I have driven this way for a couple days so this might be what I settle with in the end. I have one more thing to try... adding weight to the flaps from the inside to see if I can keep the flaps from opening unless the pressure in the cab exceds the weight I add.






You can see the thin rubber flap that separates the inside and outside of the cab in the following two pictures (looking down into the vent).

 

If you want to see if you have it or not, look between the cab and the bed of the truck. There will be a little box extruding out centered just below the rear window. Have someone shut the door while looking at this box. A flap should open. The problem is that the flap just randomly opens when driving down the street.

 

I did not feel or hear any reduction in the air coming from the vents when the fan is on high in fresh air mode. I tested the difference of window closed and window open while the vent was taped up.

 

Results - Day 2
I taped up the vent with double the amount that was already on it. I made sure that there were no gaps at all. This time I did experience a pressured cab. The AC/Heat fan speed was reduced by almost half. The second I turned on the AC/Heat I could feel the pressure in my ears. Shutting the door still was no problem though. The windows did not fog up either. I did not test the windows being open to see how much inflow there was but I will try to do that on my way home from work today.

In general the road noise was reduced in half and the the air rushing noise was almost eliminated after plugging up the vent. From the vent there was no noise at all.

Next test will be to push some foam down in the vent. My thought on this would be that it will reduce the noise but still allow some flow of air. If this holds true then the AC/Heat should run full speed.
I am also considering a way to hold the rubber flap down unless there is higher pressure in the cab. As I mentioned before with the AC/Heat off and windows closed the flap opened up randomly down the street and stayed upen for most of the time. The pressure in the cab should not have been changing much at all. Actually when I felt the vent when this occured it almost seemed like the air was being driven into the cab, not out of the cab. I was thinking about a rubber band or a some double sided tape. Any other ideas?

 

Hmm, I dont know. The noise coming from this vent is so annoying that it drove me to do this experiment. It is possible that the flap on mine is defective in some way.

 

This is definately a good idea. I dont have the wheel weights though but I could try adding weight in some way to hold it down. Might be difficult reaching down between the cab and the bed.

 

So you kept your closed up huh. Like you said, I hope that you dont find your closed up vent an issue after reading this. I am hoping to come up with the best solution with my experimentation.

 

05Moose: I tried the shutting of the door and found out that I dont see it flapping open either. I looked and felt the thin rubber flaps in the vent that separate separates the inside and outside of the cab and found that they dont open up far enough to see from the side of the truck.

 

See post 1 for updated results (3)