removing power steering pulley

97 silverado 350.

Can someone please tell me how to remove my power steering pulley? The shaft has a internal 3/8 hex head. There seems to be some sort of retainer on the shaft after the pulley. Is this threaded on?

Thanks in advance

It may be threaded, but most that I've encounted are pressed on. If it is pressed, there should be no threads evident on the inside of the sheave bore. You can use a puller to remove it:

http://72.19.213.157/files/SheavePuller.jpg

The inside thread is used to press-fit the pulley back onto the PS shaft.