Well, w/ all the braided lines.
In a nutshell:
If you have a cooler in the radiator, you want to run the line (output of trans) thru the radiator, then thru the external cooler. The return line will run from external cooler back to trans.
If no radiator type cooler, then it really doesnt matter. Just run the line to the external and then back.
YOu will know which line is the output of the trans by running the engine for a few minutes, put it in gear then shut the motor off and see which trans line is hotter than the other. Dont run the motor long or both will seem hot. Or, do it the messy way and remove one of the trans lines and see which way the flow is. Do this for just a split second as to not harm the trans. I really dont recommend this way, but it should work.
It doesnt matter which line goes where on the external if that is all you use. The flow in the external cooler is not important.
SgtDel
aka "Andy"
www.delbridge.net
1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4