I have a '15 5.7 w/ the 65rfe, I'm trying to install an add-on trans cooler in addition to the stock AC/Trans combo unit. I'm trying to find out what the thread fitting size is for where the quick connect threads into the side of the stock cooler. It appeared to be 1/4npt, but when I tried that, it was a bit loose and wiggly even though the threads were just close enough to engage. Could it be something like M14, or is there something else a little bigger than 1/4npt? I'm just looking to thread a barb fitting in there to clamp the cooler onto. (Adding a hayden 679 rapid-cool) Thanks for any insight here.
Could it be as simple as going up to 3/8? Would the threads on a 1/4 engage on a 3/8 opening?

 

So it turns out, I didn't even need the fitting, because the stock cooler is shot. My neighbor across the street owns a shop and stopped and helped me out and noticed the lines were nowhere near as hot as the pan. We put a clear tube jumper between the lines and it flowed fine and got blazing hot fast. So we ended up just running straight through the new cooler and bypassing the stock one. Trans temp dropped 15deg within a few mins.
I drove a 2hr round trip drive today and saw it hit 225, I thought that seemed way to hot not towing, now I know why. Most people say these 65rfe's are solid and run 140ish give or take during normal driving.