What he's describing isn't a true 2wd low, but a little trick. It is more or less the equivalent of unlocking one or more of your hubs on a 1st gen and shifting into 4wd low. But on a 2nd gen, the vaccum disconnect engages the front shaft when shifting the tcase into 4wd. By defeating this and operating it manually, you can still shift into 4wd and keep the front axle shaft from connecting. The front output of the tcase is still turning, but power isn't being transferred to the front wheels. It also only works if you have an open diff. Add a front locker, and you'll find yourself in 3wd low range rather than 2wd.

-Rob