Wont go into or slips out of gear

My o6 dodge grand caravan wont go into drive even while
pushing on the brake. It'll go into park neutral and reverse
just fine, when it does finally go into drive it will slip out
almost like I'm in neutral. I have to put it in park and start all
over. By the time it actually works it'll kinda jump when in
gear. I've had to do so much transmission work to this van
I'm at my ends trying to figure out what it is this time.