Got a new truck this weekend

[cochino12]

I went in for a couple happy hour beers and the bartender told me she had an old truck she needed to get rid of. She said it didnt run because the battery wouldnt charge and it wouldnt shift out of 4 low. I showed up slapped a battery in and it fired right up, runs pretty good but something is wrong with the t-case, it pops out of gear and wont engage in anything but 4wd. Any ideas how to fix it or would it just be easier to grab another 208 and put it in? The exhaust was done last year, motor was supposedly rebuilt, and the best part NO RUST. I think I got a pretty good deal at $1400