Answer
Fordbloke is right. more than likely it is the modulator. it takes about 5 minutes to change. simple its located in the lower rear of the tranny. it will have a vacuum line running to it. their is a simple check. unplug the vacuum line (if tranny fluid runs out the modulator is definitely bad). plug a hose into the modulator that is long you can suck on it. if there is no resistance (you just suck air) then the modulator is bad. this is a simple check/fix and will save you a bunch of money if it is only the modulator.