Recently it seems like my rear window (the middle slidder window) seems to be making some noise. There is about 1/4" or less movement when it's closed tight.
I'm not sure that's the noise. It's hard to tell when i'm driving and can't be in the back to hear it. I know, I need to let somebody drive my truck and sit back there. It's just been hard to to connect.

 

I have heard this too in mine. I think it is the window kind of hitting the weatherstripping making a clicking type of sound. I just open it a little and close it back down again to correct the sound.

 

I get this every once in awhile too. Interestingly it seems to only happen when it is a certain temp outside. Between 45 and 30F. Warmer or colder and it seems to fo away. Must be contraction of the rubber seals. I just put a folded piece of paper in the latch to make it close tighter if it really gets to me.
Deck