steering gear box help!
 

So far I've gotten the steering gearbox off the Yota and Ive disassembled it, but I can't seem to get the worm shaft locking nut to turn loose with a screwdrive/hammer. I know that its punched down to lock it but I've smack that out of the way and still I can't get the locknut to turn... Am I doing this wrong??
https://cimg9.ibsrv.net/gimg/www.yot...c41920d540.jpg