The 4Matic system on the 1999 is vastly improved over that on the W124 systems.

However, if something does go wrong, repair costs are very high. The transfer case, front drive shafts, front differential are all high price items. Common problem at high mileage is slow weep in the transfer case (not a big deal if you can tolerate a small leak and you can add fluid to it) and torn CV boots (causing CV joints failure).

Overall, the system is still pretty reliable and a wonder to drive in snowy winters.