904 Transmission Stopped Going Into Gear

Did you check the governor valves to make sure they move freely? It's probably okay; TFs don't have a lot of valve problems. You should get a TransGo shift kit because the instructions will help you assemble the valve body correctly plus they have a new manual valve that allows the pump to charge the converter in park. It will still leave maybe half a quart up the stick, but that's still ten times better than having to go to neutral for the charge. They're $26 on ebay free shipping. If somebody put the wrong thrust washer in there, I wonder what they did to the valve body.