case 580 sk

Hello, everyone I have case 580 sk I pulled the backhoe up on a slight hill and parked it there for a few days jumped in to move it would not move in forward or reverse hooked truck to it and got it on level ground nothing. So then decided to change the trans axel fluid and filters found and checked the screens in the line were nice and clean. I tried again nothing but when I checked the new filter there was no fluid in it ? that's where I am at no forward or reverse also I let the backhoe run to warm it up thinking could help nothing could this be charge pump whats next inline to check out thanks mike

case 580 sk