Auto Trans not shifting

I have a 2000 GT, Automatic. It shifts when I drive REAL slow but at half throttle and WOT it won't shift from 3-4(?) @70mph. It just bounces off of the Rev limiter. I checked the fluid lvl and disconnected the battery to reset the pcm. Any advice? Thanks,
~Jason

I have the same problem. I have to let off the gas to get the tranny to go from 3 to 4 which is the torque converter lockup. I've spoken to others and they say their cars are the same way. I guess I can live with it.

Even If I let off at 70 it won't shift till it spools down. I can't live with that. It's only started doing it in the last 48 hours.