HELP 727 trans problem

Are you checking the fluid in neutral? If your checking it in park it'll read full when it's not cause they don't pump fluid in park. BTW: is it a stock torque converter? If not what is it? I'm asking that because you said it revs to 3500 before the truck moves. The only way it'd do that is

1. you have a high stall converter or

2. it's not pumping fluid.