The NV-242, which has 2WD, 4WD Part time, 4WD Full Time, Neutral, and 4WD Low Range was a rarity in most ZJ'* and WJ'*. You could mostly find them in the Laredo base models with the I6 engine, but a few of the V8'* have them, too. Part time and full time are the same gearing. Full time mode passes the front output thru an open differential in the t-case, to allow the front and rear driveshafts to turn at a different rate (just like an open diff in an axle). Part time locks that center diff, to provide a non-slipping output.
Most of the V8 models have either the NV249 or NV247, which are the fulltime 4WD cases. The NV249 in the (1993-199
ZJ'* has a viscous coupling which does go bad after a while and will cease to allow slippage between the front and rear driveshafts. The NV247 uses a georotor pump to progressively engage the front driveshaft as needed. I think the 247 was just in the WJ'* (1999-2004).
The NV147, which may be found in rarity in some 2004 laredos, should have never been made.