In this video, i go over 2 very common problems with the 6L80E that would cause no forward movement. First is a shrunk down #1 checkball and the 2nd is a cracked 1-2-3-4 clutch piston, in this case i have a cracked 1-2-3-4 piston, GM knows about this and updated the clutch piston, recommend installing the updated piston on every overhaul. Thanks for watching. Happy Holidays to everyone.