Gear stuck in 4 lo

Has the transfer fluid been checked and replace at least every 30 miles? It may be sticking. The case takes ATF type DEXRON VI

check the fuses as if the brake light fuse is blown it won`t allow the shifter to move out of park.it has a shift interlock system so the gear shift won`t accidentally be moved out of park by mistake.

That maybe the case however I would check to make sure the linkage from the 4wd shifter did not pop out from the transfer case first.

4wd auto: you can shift into this mode at anytime. it is good for conditions where you might need 4wd.
4wdhi:: you can shift into this at speeds up to 30mph and both of these back to 2wd while in gear.
4wd lo : stop vehicle and shift truck into nuetral ok to be rolling around 3mph shift into 4lo then put in gear same when shifting back to 2wd

your high low range shift solenoid is out!! change it!

@ 2000 gmc: Exactly right.

asker: Also, it helps if you're rolling at about 2 mph with the steering wheels straight.
You cannot shift into 4LO with the wheels turned or when in a drive
gear. Also, it may be that you need the electric shift unit serviced.
It is not recommended to drive on dry pavement while in 4LO.

Either your linkage is not properly adjusted or the shift fork is a bit worn inside the transfer case. I have a bit of wear on my own and shift into low range while rolling with no load, between 5&20mph and it works fine except that I need to anticipate needing it before hand. One important rule...If it grinds, don't force it into gear. That will cause damage.
Also, if you just got it, change the oil in there...you have no idea when it was last serviced.

shift from 2wh to 4hi to neutral then 4lo all while in drive and moving slowly. The owners manual and repair books say you can actually damage the transfercase if the jeep is parked. You can go into 4hi at any driving speed, just not too fast!

something has broke inside the transfer case keeping it from going into any other gear

The 4-lo is so low that sometimes you really have to push it to go into gear. Put the transmission into neutral, and even let it roll a little bit to get it to slip in easier.

You could try to turn the engine off as well while you're in neutral, and then put into 4-lo.

If it's impossible, I'd have your linkage checked to make sure nothing flew up in there and is stuck and/or it's bent.