Trans fluid flow direction.

[Tractoman]

I am getting ready to install a tranny cooler and want to plumb it in after the in radiator cooler and before the fluid goes back to the transmission. Is the upper or lower cooler line on the radiator flowing back to the trans. Cannot find a diagram of the 6L80. It's on a 2009 Yukon XL SLT.
Thanks,

 

[Buzzcut]

Usually the lower line at the rad is the transmission "out". I don't expect GM changed this pattern.