when i replaced my gear box both my old and new one i could turn the pitman arm by hand

 

And as I said, so could I, when I just jacked up my van. And as I said, it was a lot harder turning the box via the pitman arm than it was via the wheels. I repeat my previous observation that I'm not exactly sure what the OP experienced when he tried to do the same, and repeat my contention that it's possible the conclusion of "stuck steering box" was reached partly due to a misunderstanding of how a vehicle whose power steering has failed compares in steering ability to one with manual steering.