I've been trying to get my C-6 adjusted and running up to par. I've heard about adjusting the vaccuum modulator, but my Hayes manual does't say how. I saw on the internet HOW you adjust it with a screwdriver, but not why or how it effects proformance. Can any one out there tell me more about this adjustment, what I should look for. I could find out by trial and error, but I'd rather not. Thank for the help.

 

[updated:LAST EDITED ON 20-Jun-02 AT 07:55 AM (EST)]The trans is basically a hydraulic computer-a stupid one, but one none the less. It 'knows' road speed from the tail shaft driven governer.
It 'knows' throttle position from the kick-down lever or the throttle
lever depending on year/model. It 'knows' engine load from the vacuum
modulator.
The governor is always trying to upshift to a higher gear. If the vacuum is LOW, (full throttle), the modulator 'WINS' and keeps the
trans in lower gear, within limits. If the vacuum is HI, as in at
slow accel or cruise, the governor 'wins' and shifts the trans up a gear.
Older trans used 'throttle pressure', variable over the full range
of the throttle position, to modulate shift oil pressures, and thus
the shift hardness. They also used vacuum modulators, I *think* that
the vacuum was the rpm/mph variable, and the throttle pressure was
used to make the shifts harder/softer, and to force downshifts...
Probably more confused now than before, huh?
Basically, you turn the screw in and out to adjust the spring pressure within the modulator. dont ask which way, i never remember.
changing the spring adjusts how much the modulator will move a pin and thus a valve spool against spring pressure in the trans at a given vacuum reading. Modulators can make a car shift sooner than normal,
or if bad/disconnected, the trans will tend to shift way late, much as if the throttle was to the floor, come to think of it...
tom