TCC won't disengage?

My 95 Astro van has been acting like it isn't shifting down when I come to a stop. I've had to shift down manually and then it seems to be starting out in 2nd gear. When it shifts, it bangs into gear. When I start out in the morning it starts in 1st gear, but still shifts hard. It finally occured to me that maybe the torque coverter clutch isn't disengaging once I get going. Is that possible and what can I do about it? The vehicle has 259,000 miles on it and I just changed trans oil and filter.

It could be the TCC or the pressure modulation valve sticking. Running full line pressure will cause very hard shifts and engagement. Did the problem begin after changing the trans oil and filter? If so, you may want to revisit the filter and make sure the seal on the pickup tube is properly installed.

The transmission was acting this way before I changed oil and filter. That's why I changed them. I was hoping new oil would solve the problem. No such luck.

How does it act if you manually start in "1" and manually shift through the ranges at the appropriate speeds? Is there any delayed engagement into any of the ranges?

Transmission problem solved!! The solution was the result of solving another totally unrelated problem. I started out for work yesterday morning and the engine died two blocks from home. The engine would turn over but wouldn't start. I discovered a blown ecmign fuse. Put in another one and that one blew. Instead of going to work, I spent the day trying to find a short in the wiring that the fuse feeds. The problem turned out to be a heater hose pressing down on the bundle of wires that come out of the firewall next to the alternater. I didn't find any bare wires, so I used a nylon tie to hold the hose away from the wiring. I also loosened the tightly bunched wires and now the engine runs and the transmission shifts properly.
PTL!
Thanks for your responses blue bowtie.