Transmission cooler line plumbing '08 Exp 3/4 Duramax
 

Has anyone else done this? Gotta admit, I'm having a hard time with it, what is the normal procedure for running these lines? I really am at hard point here, the fitted lines don't want to pass through, I'm hoping I don't have to remove any real elements.

unplug return line from radiator and plug it into aux cooler output. Install new short line from radiator output to aux cooler input.

Just did mine
 

I just got finished doing mine feed the line from underneath towards the radiator. If you're having trouble removing the old lines from the radiator cut them off a couple inches from the radiator and unscrew the whole thing. Then you can remove the line easy. Then screw the connector back in tight before you reinstall.
When you reinstall the new lines be sure to put the clips in first then just push the new line in until you hear a click.