110 Engine Vacumn Diagram
 

I have a 1980 280SL Euro car. Right now she suffers from hard shifts. It's my feeling that this is probably due to a vacuum problem. I had some work performed by an indy and the problem arose subsequent to that. Additionally, there was a vacuum port at the rear of the intake manifold that was open. Any help or suggestions would be deeply appreciated. Thank you in advance!

Maybe the feed to the transmission modulator was knocked off during service. No vacuum to the mod equals hard shifts