Here is my transfer case 4WD vacuum switch .
I understand that the red line should supply constant manifold vacuum to the 4WD vacuum switch.
I cannot trace the red line to its vacuum origin .
Any guidance on tracing upstream back to the manifold carburetor vacuum source? I believe that there is supposed to be a vacuum reservoir in the upstream source. I cannot reach this red line without taking it to a service garage / lift /remove transmission support brace. ( $$$). Where does the red line plug into the reservoir ? Where does the red line plug into a tee'd manifold vacuum source?