If the car starts out in the position the shifter is in, the kickdown most likely is not your problem if you say it shifts fine manually. It sounds like the valve body was modified for full manual shift. If the shifts are nice and crisp when you shift it manually, this would be my bet, as the tv pressure would be jacked up in the modification. If this is the case, you will have to shift it manually so you don't smoke the trans, or put a regular valve body back in it and eliminate the solid rod in the servo if it was installed, along with the proper kickdown setup.
