Maybe rust or buildup in the spline. Use a good penetrant like PB blaster and drive one 1/2 way BACK. Then see if there was a ridge of crud in there. Scrape with a thin tool/razor. put some never sieze in there, dilute with PB blaster, heat it, try again.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.