As Rockyridge mentioned, just use the stabilizers to lift the hoe to the correct height. I have never been able to do it with just the 3PH alone. It's so much easier with the stabilizers, I don't know why JD doesn't just tell you to use them in the manual. I use them for removing the pins also, just be sure the 3PH is raised fully before raising the stabilizers....
With that method, I can remove or attach the hoe in a minute or two...