Long story short, I pulled the pump out to replace the gaskets and seals. It's a 4R70W from an '02 Mustang GT. When I pulled the pump off, some of the packs became misaligned. So I was trying to jiggle everything back into place and this clip popped out:
Any idea what it is? Pretty sure it came from inside the transmission, but I can't find it in the manual anywhere. I already pull the trans from the car and pulled off the valve body and over drive piston so I can get the stack aligned properly, but no sign of where this clip came from.