This seemsto be a common problem with WJ's - you shift the transfer case (Select-Trac) into 2WD but the transfer case stays in 4WD.  This is due to a number of factors listed below.

While in 4WD, coast under 35MPH in a straight line. While coasting, put the tranny into neutral and wait a second or two before putting the TC into 2WD. Wait another second or two (you should still be coasting straight). You may hear a "click" from the TC lever. Make sure you can get back into 2WD and drive around without any problems.

You can also do the above procedure by putting the TC into 2WD first, then put the tranny into neutral, and wait a second or two. You may hear the click

If the above doesnt work, then you may have a linkage problem

The issue with it getting "stuck" occurs when you have different tread across your tires, different tire pressures across your tires, different size tires, or a combo of them. You need to remove the pressure placed on the TC in order for it to shift properly. This is done by shifting to 2WD and placing the vehicle into neutral