727 problems, opinions wanted...

Over the years of building 727's which along time ago i worked a a shop that did all the mech. work for Hillsborough Co Fl. Sherrifs Dept. This was a common sign in 727's. I found it to be piston seal leak by on hardened seals. When we would rebuild these trans. the problem would go away. Since you have movement in neutral, I would think the shift selector valve is out of position.