C-5 question

[Broncodude]

Does the C-5 have a vacuum modulator? Where does the line hook up too?

 

[Mutant Pony]

Yes. The line hooks to manifold vacuum.

 

[Will]

meaning you should feel it sucking when you put your thumb over the port when the motor is at idle.

The tranny uses the modulator to adjust the hydraulic pressure to the clutches. When the vacuum in the manifold drops, the tranny knows the throttle is open so it increases pressure to make the clutches hold more firmly. At light throttle, it uses lower pressure to make the shifts smoother. Higher pressure (low vacuum signal) also spaces out the shift points.