Ki-Lo shift will rotate but acts like it's in neutral

[Gitche Gumee Kid]

I-H 284 ( 1980 year ) 4wd diesel. I can see the shaft rotate so I know it;s not a sheared roll pin. Problem in the gear box ? Can the top cover be safely removed for a look -see?

Any suggestions are appreciated.

GGK

ETA That's suppose to be HI-Lo shift ^^^^