i had an auto glass guy i know test my truck for leaks and he determined it was leaking around my rear window and since my rear end sets higher then the front end it was entering the head liner and flowing down the corner windshield posts and soaking the front floor as well as running down the rear inside and soaking the rest of the carpeting. he removed my rear window (which is a slider) but not sure it made a difference? he discovered unfinished weld seams where the cab is welded in the center and ends at the rear top, also had water in my top cab break light. he removed the the light as well and finished the weld with a non-silicone sealant (silicone eats metal) resealed both the light and window and so far so good....seems as though problem solved! it has rained heavily here since the fix and i have not had an issue and the guy and his son who repaired my truck have encountered this in the past and know what they're talking about....hope this helps? i was about ready to get rid of it but i do enjoy my Colorado.. as for any cooperation from the dealership on this isuue? good luck, they treated me like a chump at every dealer i contacted and act as if no one has ever complained about this problem before....i will never buy another new vehichle unless its a Harley!