99 K3500, crew cab, diesel dually.

I just replaced the seized motor in this truck. The new engine runs great however, I put the truck into drive and hear nothing but transmission noise in D, 3 and neutral. Reverse, 1 & 2 don't make that noise. The transmission will not engage to move the truck.

I did replace the internal rod that attaches to the neutral safety switch but not sure I got the spring re-installed correctly. I replaced the fluid and filter as well.

Anyone have any thoughts or ideas?