Hi
Did you clean out the suction screen? Is it proberly reinstalled? Sounds like some air in the system to me also. I've not had that happen to any of my JD's doing fluid change for the universal sump.Perhaps with the loader on and connected, tractor off, crack one of the metal fittings to a hose going to the cylinders up front to let out the air. Start it for a second and bleed it. Shut it off and tighten the line. Stay away from the line when it leaks. Perhaps that will help get the air out.
Steve