1. Go to hardware store.
a. 6' of 1/4" steel cable.
b. 2 cable clamps
3. Crawl under the Jeep with the stuff you just boutht.
4. Loop one end of the cable around top of the passenger side frame rail at the transfer case yoke area.
5. Use a cable clamp to tie the loop together... and tighten the clamp down.
6. Loop free end of the cable under the yoke and arund top of the drivers side frame rail.
7. Use the second cable clamp to secure the loop to itself.
8. Tighten the cable clamp.
9. Recheck your work.
Remember to keep the cable taught. If you've done it right the cable will now support the drivetrain.
I always use this method to support engines, transmissions, transfer cases, or whatever needs supporting. This frees the area up under the supported device so I can crawl around unencumbered. There's no jack or no jackstands to have to work around.
It works quite well. I uaually have about 4 or 5 of these 6' cable pieces laying around. They're really quite handy, as I use them all the time.