Transmission Slipping

I have a 2001 Pontiac Grand Prix SE 3.1 V6. The Fluid had not been changed in this car for 126,000 miles, one day resulting in some hard shifting. This soon turned to the transmission sticking and not shifting terribly when cold or sitting for a while. When it finally starts to grab and not stick it will shift hard. I changed the tranny fluid and filter, just from the pan not the catverter. I imagine its a sticking solenoid or damaged solinoid or vacume line causing the problem or valves sticking. I already have one bottle of Lucas Tranny medic, did nothing.....im gonna put a another bottle in, would this be a bad idea? at this point i dont see what else i could possibly damage. The wiered thing is it will shift fine sometimes, so it cant be a mechanical problem.

have you ever tried to shift the car manualy?
putting it in first and then start to drive, manualy put it in 2nd. then drive and overdrive?
Lucas is only going to cause you a problem I believe. I deffinatley wouldnt add more.
Not that it wont help a lost tranny or engine get get a few more hours/days or however long of run time. but I would never use it.
Just for chitz and giggles, check the detent cable leading from the throtel body.
Has there been any work done on the car recently?
How did the problem come about. just happened or a slowly getting worse condition.
this could also be associated with a blown gasket in the valve body.
Make sure the electrical connections to the tranny are clean and tightly connected, no pinched wires, burned or worn/rubbing situations.
just something to think about

yea i was thinking it could be wire to....i'll look into it

GARY, Im confused. Does it slip or shift HARD? If it slips unfortunatly its probably time for a rebuild. If its shifting really hard, I would suspect a problem with a pressure control solonoid in the transmission. This is also not a DIY job. My other car had a problem with a PCS. out of the blue would shift fine, then it would just all of a sudden just SLAM into all gears. I just urned the baby off and retstarted and it would be good for another 5 months or so where I would just turn it off and back on. WIERD!

GAS, his trans is electronically controlled. I dont think it has a throttle boost cable coming from the throttle body going to the transmission.

I know, im getting pissed to......it does both. It "sticks" doesnt slip really. LIke it will just get stuck in 2nd gear and going up a hill the RPM gauge will go all the way to 5,000 and wont gain any speed casue the trans is not shifting, then after all the "sticking" it will start shifting on time but kicking a bit when it shifts(somewhat hard shifting)