I have a 4.8l v8 and 4l80 transmission, bought the van a couple months back and been having a transmission problem since purchase.

Originally I planned on just putting a new transmission in, but now I'm leaning more and more toward the transmission not being the problem.

Van starts fine, and the Gear indicator on the dash displays P, when shifting into any other gear, you never know what the display will read, but it rarely ever reads N, if you are in N, it usually displays P.

When putting the van in D, most of the time, the van displays 2, and then if you sit there long enough, or rev the engine, it will bump into D and begin to move. Once moving, the van shifts through all gears, however does seem like maybe its light on line pressure. I have been very easy on the van, simply because i don't want to cause damage due to it not functioning properly.

When shifting into R, it usually displays correctly, but may be hesitant before actually moving in reverse.

Things I have done.
Replaced transmission fluid, and filter.
Replaced internal pillow switch
Replaced transmission internal wiring harness
Replaced neutral safety switch on side of transmission

The NSS that I installed was removed from my parts van, which I confirmed displays all gears properly before removal.

Does anybody have any thoughts on what could cause this?