At the risk of being thought a complete moron, I have to ask if there are vents in the back of the 99 extended cab. I recently bought a 99 z71 and am getting bunches of road noise from the back seat area. I've checked the windows, they're loose but not the source. From outside, I can see what look to be vents between the cab and bed but cannot tell if they are open and cannot find them from the inside. HELP!!!!

 

i say your door r not shuting write i do it all the time if the 3rd door isnt shut right u get alot of niose

 

there is 2vents in the back of the cab one on either sidei have an extended cab with no back seat when i first took the seat out there was substantial noise because the seat absorbs most of it but i dynomattedover the vent holes and that took care of the noise

 

If the windows are loose then you would hear like an air leak. Atleast that is what mine sounded like. So the dealership tighten them up with some long screws through the latches and into the door frame. Does it sound like a roar from the tires? If so are your tires worn out or maybe they might need to be rotated and balanced. Anyhow that is a couple of ideas to look into.