I've always used some form of penetrating fluid, then try to turn nut both directions, sometimes tightening it more will help it break loose & sometimes i find it was a left hand:confused3:
Kubota M7040, Kubota MX5100, Deere 790 TLB, Farmall Super C
I have not read these posts and it probably has already been mentioned but make sure you don't have a backwards nut. If they won't budge, this is often the reason.