Rich80

Havent climbed under there to look yet but is there a vaccum line running out of the modulator and where does it route too??

kenincanada

should come out of mod. and directly to intake man. behind carb.

jerryp58

Agree with kenincanada.

If I remember correctly, it shoud be the hard line connected to the center of the vacuum T on the manifold via the rubber hose (directly in front of the distributor in this pic http://users.erols.com/jerryp58/corv...underhood2.jpg) . The hard line snakes its way down to the modulator where it is connected to the modulator with another short piece of rubber hose. My top rubber hose was in pretty bad shape.

If you're fiddling with the modulator, you should really consider an adjustable modulator which will let you modify the shift points. It made a nice difference in my trans especially with the B&M shift kit :yesnod:

Hope this helps.

AlwaysWave

Are there different types of adjustable modulators? I suppose they're listed for the trans type like TH400, etc?

Jvette73

There are different types. They are identified by a colored band that runs around them. I suppose the differences would be mainly in the tension of the spring inside the modulator. Each one is adjustable within a small range up to 5mph: Starting with the correct one could be an advantage. The higher spring tension modulators will tend to shift later and be adjustable on that later shift range. Modulators only controll the part throttle shift points. No modulator will effect the full throttle upshift point. That is controlled by the govenor. My old TH400 adjustable modulator has a red band around it. This one worked well for me. I turned the screw in(clockwise) one turn and took it for a drive. i continued to do this untill I got it where I wanted.