I have a 2000 Dodge Ram van 5.9 that I'm adding an auxiliary trans cooler. Already have it mounted, just need to know which cooler line from the bottom of the transmission is the return line to the trans. Looking at the front of the van, it seems like the line on the passenger side is the return. I want the fluid to go through the radiator first, out of the radiator into the cooler. Thanks

 

At the trans, the rear line is the return line.

 

You posted in the truck section, This is what the lines look like on a truck.