727 slipping when hot

I have been fighting trans. issues for a while now thought they were all straightened out. Got the Duster out for the first time this year a couple days ago, worked great for a while nice firm shifts but after 5 or 6 miles when i would stop it would pull out fine but when it went to shift it would start slipping i put it in neutral then back in gear again it would go until it went to shift and would slip bad.
I'm not a trans guy by any stretch and talked to a few guys about it i been told it could the front pump, the accumulator, the valve body or even a crack in the case.
The fluid is full, that was the first thing i checked, can anyone give me any better ideas before i pull it out again?