Truck won’t move under power

[Iamconfused]

Hey guys I have a 2001 Silverado 5.3 liter with a 4wd 4L60e and I am at my wits end. The truck will accelerate but will not move. I drained the trans fluid and it was black so naturally I decided to put a new transmission in it hoping to fix all issues. After installing the new transmission the truck was having the same problem as before and now it wasn’t showing the correct gear for the where the shifter placement was. Then I put a new neutral safety switch in the truck after it was suggested to me by a friend. I know the rear end is fine and I know the torque converter is seated properly. This vehicle is very important to me please help. 

[CamGTP]

So it doesn't move forward at all?

 

Or it does drive but it can barely get out of it's own way?

 

Does it roll freely? Like no stuck calipers. It could also have a plugged up exhaust if it can't breath.