Classic/Antique Car Repair: 1965 chevy - 350 turbo trans. problems, manifold vacuum, vacuum modulator

Question
multi-part question:1.I have 1965 c-10 w/350 turbo trans. Slips in second very little jerk when shifting...leaking fluid badly...not sure from exactly where...Also I don't know what the "thing" is on the back of the transmission with the hose or line coming out of it., it's really loose!!!

Answer
The thing on the back of the transmission is the vacuum modulator valve. It reads the engines manifold vacuum to determine shift points. As far as the slipping as leaks go it sounds like and oil pressure test is in order and probably a removal and overhaul.
Brad