2006 Chevy Suburban mystery leak

Transmission problem
2006 Chevy Suburban V8 Four Wheel Drive Automatic 121k miles

excessive leakage of atf was noted several months ago. Replacement of any suspect gaskets and seals including pan gasket has already been done over the months. Each time a repair is made the leak seems to subside until I make an out-of-town trip that requires about 2.5 hours of freeway time(usually gets repaired 1-2 days before trip. Sorry, no extended city driving). When I check the underside of the suburban mid-trip. The leak has returned and yields a red drop from someplace on the pasenger side of the vehicle about every 2-3 seconds immediately after stop. Also the underbelly of vehicle is coated in atf (from high speeds). While I could never pinpoint the leak, I have recently noted that the origin seems to be located near or inside the frame of the longitudinal beam(extends the length of vehicle) on the passenger side near front wheel well. Perhaps a coolant line? Technitians claim they are fine but I am always a skeptic. Any ideas would help