I found that my transmission wouldn't lock the Torque converter as well after it heated up, almost like the the lock solenoid was failing but after a whole ordeal with waiting for the right part and still getting the wrong one I was looking at a picture of a valve body online and noticed that one was missing.

Pic of the one that was missing in red.
I recognized the screw because when I bought the car it was in the ash tray...

the screw


So yeah I put it back in and Bam it was fixed.

My theory is that when it heated up it allowed the valve body to flex just enough to let pressure leak out.


The other screw that was in the valve body, this one was still in there.

Better pic of the one that was missing.

 

Hmmmm interesting!