Help to figure out which line is pressure side
 

I have a 06 f150 4x4 4.6 with tow package.im upgrading my transmission cooler with one that has a fan. I'm trying to figure out which line is the pressure side from the transmission.looks like it runs from the tranny to the radiator then back out of the radiator and then to the factory cooler and back out and back to the tranny.im not sure if it goes to the cooler or the radiator first.any help would be appreciated

It goes to the radiator first.

The first one that warms up when the vehicle is first started.

I could be wrong. I thought it was the line that connected the top of the radiator. So that hot fluid goes in through the top line, gravity allows it to feed to the bottom line. Since heat rises, thermodynamics would allow better cooling as it is going down. Then the lower line feeds it into the auxiliary cooler, then back to the transmission. The logic would be to look at the transmission cooler for the line which connects back to the transmission. Any aftermarket cooler would go inline between the OEM cooler and the transmission return. But I am probably wrong. There are transmission experts here who know far more.

Mark Kovalsky is/was a Ford transmission engineer. From what I understand, he helped design the AOD, 4R70W, 4R75E, etc.

I was a Ford transmission engineer. I worked there from 1988-2007. I worked on the AXOD, diagnostics, the 4R100, the 5R55N, the 5R110W, and transmission cooling. I never worked on the AOD or 4R70W family.

I always thought Mark's former job was fascinating.

Just to know that those transmissions he mentioned above are used in a variety of vehicles that he sees around town every day, and he had a piece of the puzzle that he worked on.

Like I said, that's a neat job!

It's even more impressive is that he shares his knowledge on here when he can.

Ah well, I was close. I knew it was one of the auto's, just wasn't a 100%. I tried.