Another T-Case problem

[JoeM]

Have an '89 K2500. 5.7L. Should be NP241. Sometimes it's hard to get the shifter into 4hi from 2hi.. If I try to go into 4lo, grinds like crazy.. The one time I did get it into 4Lo, couldn't get it out. Had to shut down the truck, put in Neutral, rock the truck a little and force it out. Don't need 4lo but I was just testing it.
Safe to assume b/c of the grinding and hard engagement, t-case is toast? Maybe shift fork or bad chain??