Rear Diff Locked out possibly

So I'm in the middle of changing my clutch and brakes but we didn't finish. They didn't want me to keel the car on the lift so we had to roll it out. The tranny isn't in and the front axles aren't in, and the rear axles are. So in when we were pushing it back it locked up out of no where. My best guess it's something with the rear diff bc the front axles aren't attached to anything. The e brake isn't on either. Any ideas??? AND anyone know the part # for the front axle oil seals?

05 WRX