4WD can be used in any condtion where traction is limited. The only time is should not be used is on DRY pavement. Well it can be used but only in straight lines. Turning will put a lot of stress on the system . If it's raining outside your fine. Some older '98s have the same multimode 4WD found in the newer 4runner. If it had the 4WD button on the transfer case shifter it's a multimode system.