I think this goes in here?
 

So ive noticed a bit of green mildew on the headliner above the back ext cab window on my truck. While having to ride back there today, i decided to touch it and it was wet. Ran my finger along the whole top edge and noticed the rest was damp as well. Obviously the window seal is leaking. My question is how do i fix it? Also it is a non slider window. If I need to pop the window out to re-seal it will a slider window just pop right in? TIA

Actually I had the same problem in my truck. My window seal was leaking even though it looked like it wasn't. The previous owner put a visor over the back to cover it up then when I took it off the rain just rolled right on in.

It might be the third brake light too. You can run a bead of silicone around the seal. Obviously I'd do it so that the silicone can't be seen.

Ya, my bet is third brake light or top of seal.

Damned CHMSL!

Well I popped the light and siliconed it. We'll see if that works. The foam gasket is still fully in tact although there was mildew and gunk all along the top inside edge which was wet.

Window seal seems like its tight as can be all along the top of the window

You can pull the window seal back and shoot some silicone in there. I did both of mine.

Well, now that I have had time to thoroughly look into this damn persistent leak, I am completely stumped. I have both side panels off and have pulled the headliner away from the rear window. Headliner is soaked 2 inches up all teh way across but everything around the window and brake light is bone dry. I have run the hose on it for 15 minutes straight on high pressure at every possible angle and NO water is getting inside the cab! WTF!? Only thing I can think of is major condensation. Anybody else have this problem?

I seriously would look into your seal. Wouldn't hurt to silicone it. Mine looked perfect but it was leaking.

I also tried a hose and high psi water...never seen it leak..only wet with rain. Sealed the window and light...never leaked yet.

Well I sealed the window. Huge PITA as somebody saw it fit to use double sided tape on the canopy. Supposed to get a good down pour today, so we'll see what happens