Inspection of a 904 torqueflite

I finally took out the kickdown servo


The bore was fairly clean and didn’t have any irregular wear pattern to it-


But the servo piston was covered in black sludge. I’m guessing this doesn’t cycle fluid as much as the rest of the transmission.
Stuff like this is what I took this down so far. I also wanted to understand it. -

I’m going to start cleaning the parts with mineral spirits.