Is it the transmission Switch, solenoids? or what?

OK since ive had this car this is whats going on, say im going onto the highway right, i pick up speed it switches through all the gears smoothly but if say i have to put on my brakes and its supposed to drop a gear instead it drops all the gears back to first gear then my car jumps, and the rpm's kick up to 4-5. but i can control it one of 2 ways, say im coming up to a stop light or a toll booth, i just throw it in neutral and glide, once i come to a complete stop i throw it back in drive and it switches gears, but once i drop a gear it goes to the first gear and the switching into neautral doesnt help, so once that happens i have to pull over turn the car off and turn it back on then i can go throuigh the process of driving and naetrual switching until i accidently drop to the speed limit where the car would naturally switch gears then it jumps and rpms kick up, what could it be,
1993 chrysler leabaron gtc 3 liter v6 new head gasket water pump all new stuff only problem is this. thanks for the help
if possibel could i get the answer emailed to me at: beanzo123@hotmail.com
thanks