I've been having an issue with my 231 popping out of 2hi under load. Either wot in deep sand or crawling up a hill.. It seems it goes into neutral. Ive adjusted the linkage countless times, even disconnecting the linkage and making sure the lever is indeed fully engaged.

Never pops out of any other ranges. I just pulled the t case apart hoping for worn parts. Everything looks new, chain wasn't stretched, all shift forks looked good and their pads present. No metal or worn engagement paws. Is their something im missing or should have a closer look at? Thanks!

 

I think your Jeep is telling you to use 4WD in those circumstances

Seriously though .... did you try un-hooking the linkage and then trying it? If it still pops out, then you know its not the linkage and its something internal.