Massey Ferguson 251xe question

[tonyw1]

I need to replace the ball socket on a lift arm of a Massey Ferguson 251xe. One fell out, and I just can't get the new one in. The other side is held in by a cotter pin, but I can't force it out. It's probably simple enough, but I am doing something wrong. Any help is appreciated.
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Tony W.
Case IH Tractors