Ran my new 644 today that i just bought yesterday. worked it a little bit moving sand for a sand box. only ran it about 45 minutes. everything worked fine until i was going to back into the shed with it. it stopped in reverse, then motor quit running. It was low on gas so i thought it was out, put gas in it, started it up, engine ran fine, but no hydraulics. no loader, no drive. Checked the fluid, looked like milk. changed out all fluid and the filter, but hydraulics still do not work. never made any noises, just quit. any suggestions would be great.