Tranny mod vac line attchmts??

Vehicle is 1987 420SEL and the problem is the end of the vacumm line has come seperated from it`s original hook up and i need to reattache it. It is still attached at the vacumm modulator but not the other end. At the back of the engine I see another vacumm line fitted into a fitting with two barbed males and the one on the top is already fitted with a vacumm line to it but at the bottom is a barbed male with nothing attached. Would this be where I should attache the transmission modulator vacumm line?