MJ 88 Commanche Pioneer Tranny Problem

hi there.
I have an 88 commanche pioneer with the 8' bed. i believe this is relatively the same as an XJ.
it's a 4.0 with an automatic.

my problem is the tranny doesnt shift itself automatically, but if you move through the gears it will shift fine, but stays in that gear. from what i know a few years ago the tranny was replaced. I've been changing the tranny fluid regularly, so it's a nice reddish color. what has happened is it used to shift like sluggishly before it stopped. i was going through a toll booth and it felt like it was slipping. So dad brought it to a tranny place and he replaced a tranny computer. BAM, the thing was a hot rod, shifting just right. But that lasted for a few months and now it wont shift automatically again. So could it be possilbe that this module went again? it was a used piece.

I want to drop the tranny pan to verify the kick down cable is connected or didn't come apart.

anyone have any thoughts? or a place i can buy this module from? my dealer price was over 700 my cost (i work part time at my friends auto shop, not tranny specialists). I do not have any check engine light or anything, and the motor runs nice, has a firm shift when you shift by hand. so if you are in drive, it's drive and like a slug taking off, go to first and it's fine, just have to shift.

again, any ideas welcomed.