Getting cotter pin through ball joint

[scherp69]

So as the title says, I have a question about getting the cotter pin through the ball joint. I'm have Moog 5108 ball joints and I have the nut tight, but it hasn't gone far enough to allow the cotter pin to go through. In the past if I've gone too tight, then the entire shaft starts turning and then I can't tighten it up at all so I ended up replacing them. At $38 each, I don't want to keep replacing them. I can get the cotter pin through one side, but it won't come out the other. Any advice?? Thanks in advance.