My 2007 was leaking through the bottom of the sliding window. I read that there are drain holes that drain small amounts of water from inside the interior channel to the outside of the cab. I could not locate them but thanks to Cableguy I found my drain tubes. The drain tubes are 6.5" from the outside lower corner of the rear glass (not the sliding part but the whole real window). I never saw them from inside as they begin under the black cable guide inside the bottom tract and exit too far up under the rear glass to see. I took my air compressor and blew down past the cable guide and some trash blew out the rear of the cab. They now drain, however they do not drain quickly enough to handle any significant leaks.
On my Ram the seal or window sweep at the bottom of the sliding glass has shrunk and allows water past the sliding window into the bottom channel....causing a significant leak I was unable to locate replacement seals or sweeps and no one on the forum seemed to know where to purchase the seal or sweep (as they are called) so I had to simply seal the window with silicone....making it useless....what a shame!!! I really liked that rear window!
Apparently, you can purchase the entire lower channel which is said to include the seal or window sweep...but as I recall it is said to be very difficult to install. You can go here to order it:
EDIT: I just tried the above link and you have to input your year and model and search "lower channel" it is part #3 on the diagram and cost about $94. Still, I am unsure as to whether the window sweep is included....sometime in the past I read that it was included.
I am still amazed that the rubber window sweep cannot be purchased individually somewhere as I am sure that Dodge or what ever company made these windows uses some standard window sweep... I think that if I had a strip of that sweep I could pull the old one out and press the new one into the channel...at least it would be worth a try!!