The 249 in 97 and 98 Grands has a locking viscous coupler, that locks the front and rear together in 4 low.
The viscous coupling goes bad after a time and is VERY expensive to replace. That is why a lot of 249s get replaced with a 242 when (not if) it goes bad.
That was the case with my Grand Cherokee and why I have a 249 now sitting in my garage with nothing to do