TH350 won't kick down (no passing gear)

[RainFade]

My 71 had a th350 tranny that seems to work GREAT, no slipping, upshifts great but won't kick down.

I've done the lift the plastic tab, open to WOT push the tab back in thing to no avail, even tried it at 3/4 throttle no joy.

I assume it's connected inside the tranny as it retracts, or is this a bad assumption ?

Beyond pulling it out of the tranny to make sure it's connected to the what I understand is a springy wire sort of thing are there any other things I can try ?

This truck is new to me and supposedly had tranny work done to it in the past, could they have done something to the valve body and now it's just manual and the kickdown isn't going to work, are there common things that can go wrong in a 350 to keep it from kicking down yet the tranny otherwise seems fine ?

T.I.A.

Brian