Tractor Repair: tractor kubota 3-point lift stops after 3 min., draft control, tractor kubota

Question
Hello,
Kubota Tractor 4-w.drive L305DT (seventies model?) 3-point hitch lift will stop working after 2, sometimes 10 min. It will even dig in ( flail mower).  I'll empty it from fluid(new fluid and filter)  fill it back up and i'm ok for 2 min. I pressure checked (15 pounds) the return hyd.fluid line. No leaks. I put another older pump on, with the same symptoms.
It does act as if there's air in the system. In the past all of these measures would help. But in the past I could back on a little bump, or winch it up to lift the mower and with the handle in the up position it would stay up and I could drive off. Not now though, it plunks right back down. Oh and once and a while after waiting for half an hour it will work again for a very short period.
I'll appreciate  to hear your thoughts about this. Thanks, Rob.

Answer
Rob hi Rob with your problem it sounds like it could be a draft control problem that is if your tractor has draft control.
Draft control is for soil engaging implerments only but if your top hitch at the tractor end is in the wrong hole it can cause these type of problems bouncing etc as that is how the draft control works.
If the top hitch on the tractor has more than one hole put the pin in the hole closest to the pivot point of the top hitch or if it has a lock out put it in place.
Other than these items I can not shed much light on the problem with out some more information on what led to the problem starting.


                          Regards Danny Last