1981 Silverado not switching into third gear.

[kalbert]

Not exactly a kickdown, its a pressure regulator that uses engine vacuum to sense load. Governor pressure is applied to one side of the valves fighting for an up shift, modulator pressure is applied to the other side fighting for a down shift. This is obviously an over simplification but you get the idea. The kick down is a mechanical link that actuates a valve directly and forces a down shift at or near wot.
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