[mmcintee1985@gmail.com]

So this is what mine was like...(See attachment)
it had splines, not knurled.  If you look close you can see a dimple in which held in a washer which held in the C clip.  The C clip would move out of the way when attached and then snap into a groove when seated.  You can't see the C clip when installed.  Technically, prying it off, the C clip should release however, they are on so tight that I usually damage the washer and the C clip falls out.  
Does that all makes sense?

Update I was able to get them off. The picture with instructions about the drum elevator helped. That is the style I have. So it was just a matter of prying it off with the drum elevator still inside the arm.