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What to expect from a c6?
Howdy! So, some thread searches have kicked some ass upon multiple topics while i've been restoring my mach I, so thank you! This post is to educate my idiocy and hope that someone can explain what to expect out of a c6 tranny for someone that knows nothing about it.

As of now my kick-down works well under WOT, shifts at around 6,000 pulling through all gears. Should the kickdown only occur during WOT or when?

During normal driving conditions, my transmission shifts extremely fast, going into 2nd at 10, 3rd gear around 20mph and does not downshift automatically until idle. Upon disconnecting the vacuum hose from the modulator the adjustment screw is about 1 cm out of where the rubber tube fits over the fitting.

I know it's a seat of the pants/engine feel thing, but is this position normal position for the screw? Upon non WOT/kickdown conditions should the tranny normally downshift under any circumstances or not until it reaches idle rpm's? What rpm's does a proper running c6 under moderate (25%) throttle shift at?

Random engine factoids: relatively fresh tranny, new fluids, shift kit. 408 C 4v, 800cfm carb, midrange cam, 2500 stall, 14 warm engine idle vacum. 3.55 rear gear
Adjust the modulator in. They come all the way out, and will lug the motor. It won't want to downshift with out being forced, or near full throttle. Adjusting it in raises the shift points and makes it more sensitive to throttle input.

If that doesn't work, then it's possible it has the wrong modulator pin installed.

1973 Mach 1 Q code 351 4V, 9A paint, standard interior, 3.50 rear, C6 trans.
Here is some more info on modulator adjustment.


73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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