JustDodge

With pans using RTV instead of leak prone gaskets, one needs to use a tool like a 2" wide paint scraper to work around between the trans case and pan. Quite common to see that.
Yes some codes point directly to a converter problem and other to deep internal trans troubles. Get it back to whom replaced the trans! Even if they offer a partial coverage, it would be well worth doing.

Will do, I’ll report back and update on what happens from there. 

do a reverse flush to break it all loose

ATC auto temp control has more parts involved than just actuators like normal manual controls. This is why I suggested in the past thread to have a complete scan done relating to the HVAC system. BUT YES I agree that the heater core is a prime suspect in lack of passenger side heat.
Both my current DJ's have manual dual front zone control, BUT soon I'll be getting another that does have the ATC system, I'll post here with what I find on "real world" operation, as being in the Buffalo/western NY area....we NEED to have GOOD HEAT!

So I couldn't do it myself.  So I paid to have it done.
and here it is in all its glory.
 
 
 

I just bought some film for my back LED tail lights. 
I will post pictures if I can pull it off.