well i kind of thought that if you could mess with the kickdown switch at any time while driving you could cause some havoc especially kicking it in under full load.
the trany i have is out of a 72 olds 88 it has the vacum servo on the rt side front and on the left side near the middle is a little electrical tab. the other two bop 400 trannys i have are the same.
i think the idea of the vacum servo has something to do with the tranny shifiting up into drive from passing gear . i know my dads 74 pickup had the same type of switch cause he disconnected it when he found i was abusing the 454 in it . made the truck kind of doggy without it. figured it out pretty quick though.
urto are you shure there is nothing on the lt side of your tranny with a little wire hanging out of it. , i may be wriong