OK, simple tranny question:
At WOT(Wide Open Throttle), where engine vacuum is at 0" hg, what effect, if any, does a Vacuum Modulator have on transmission upshifting?
Specifically for the 440-T4(4T60)'s, which have 3 things that help determine shifting(TV Cable, Modulator, Governor), what determines shifting quality once the engine is at or near ZERO VACUUM?
I "think" it has to be just the Governor, but not sure?
THANKS!:)
Shift points and shift quality are both typically determined by the RATIO of Throttle Pressure (Modulator Pressure in GMs) to governor pressure. Nailing the throttle pressure at WOT fixes one side of that ratio at its maximum value, so only road speed (governor pressure) varies and it therefore sets the shift points, and the shift quality is "as hard as possible".
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