HELP 727 trans problem

I think fishy is right,recheck the fluid in neutral.Cycle it through the gears a few times then recheck the fluid,doing this a few times is a good idea.
If you tightened the rear band to much it will not make a difference on the trans mission pulling off in drive,the rear band will hold if you pulled off in manual low.
Now if it fells like the the brakes are on when you are in second then the band is dragging and needs to be looked at.

I think you are dealing with a drain back issue and the fluid is not full.