The transmission in car is a 4T60, non electronic. It has a modulator, Governor, and TV cable that controls shift timing.

The TV cable plunger is probably stuck, a common problem. With the hood open while standing at the drives side fender, look down at the transmission; that is were you will find the TV cable, a black plastic housing with a 10 mm bolt, bolted to the transmission. Take the air cleaner off and trace the cable up to the linkage, grab the steel cable and pull up on it, you should feel resistance, and release it, the cable should SPRING BACK. If the cable feels lose, the TV plunger is stuck, if so, buy a bottle of lube guard for sticking valves. Pour it into the transmission and let it circulate. With the engine hot try pulling on the cable too free it. If you can not free the cable the valve body has to be removed. Good luck.