MF 203 3 point not lifting under load?

[Viperking]

Recently bought this tractor, this is the first time using the 3 point under load. Transmission oil has been replaced.
It sounds like it gurgles when it’s at max height without load, and I can feel something pulsing/pumping when it is trying to lift the load. It can not lift a 1400# bale. I don’t know if this is normal, but I can lift the linkage fairly easily when the tractor is off.

Videos with and without load

 

[Ray,IN]

Sounds like the pressure relief valve needs replaced. If you don't mind getting your hand and arm covered with oil, the valve can be replaced with one hand and an open-end wrench. Access if via the right-side round cover that has the dip-stick, the oil level is just below the bottom bolt holes, it's awkward with only one hand but possible, I've done it perhaps 45 years ago.
The valve is near the bottom of the pump and slightly behind that round hole opening.
Be sure the tractor cannot move or start, your hand is on moving parts when the tractor moves.

If the relief valve is not the problem, the pump must be removed and rebuilt.