yeah mine is the third brake light, PO had the window replaced then they RTVd the frame with effing WHITE... ugh... still getting that stuff off the black bits. i got the truck and had the window replaced again (all good since now it looks like a new dodges single slider instead of the old school two window style it had, and i got it for $230 installed as opposed to the $500 glass shops wanted for it) then hopped ontop of her after i saw water coming in again, def the third brake in my case.

FWIW no parts stores carry that gasket that i have found. gotta goto a dodge dealership thats not closing, less one has a few in stock, mine didnt.

my truck was garage kept until feb of this year and the seal still went bad, but ya def helps.

 

The stuff I used to seal my thrid brake was called duck seal It is good stuff

 

ive got the weirds leak... got me scratching my *** in between the *** of the backseat and the back of it where the seat belts are gets soaked around the middle of it and my floors dry, my headliners dry, i checked the third brake light its still got good stripping... im lost?? only the bottom of the backseat is getting soaked??

 

Get in the truck and have someone outside the truck hitting the entire back window with a water hose and you should be able to see if it's leaking somewhere. I had a pretty steady stream coming down the inside my window in heavy rain.