I would hope it's hydraulically linked to the 3ph lift cylinders but if not, I would definitely retract down pressure before raising the lift arms. I'd ask the dealer to contact JD corporate to get the correct operator procedure but until I got something from JD, it's release the down pressure before raising. I would guess there's a relief valve that would open if you just overpower the down pressure cylinders but that's an ass u mption- not a good thing to do with stuff that is expensive to fix if you guess wrong.
Treefarmer