[Steeveedee]

Originally Posted by dmjlambert

You probably have a vacuum "tree" fitting on the intake manifold behind the carburetor. It connects there. It uses a short piece of rubber hose to connect to a metal line, and that metal line goes down to the side the transmission, where another short rubber hose connects to the transmission. I'm going from memory here, and I'm sure others will chime in if I have a detail wrong.

I'm betting that the line got bumped and is off the modulator, assuming that the guys doing the work would have caught it if it was off at the manifold. It could just coincidentally have a failed modulator, but given the timing, I'm betting that you are correct, and the line is disconnected.