The 'correct' answer is, no you shouldn't drive it. However, if you don't carry a heavy load and don't do anything that might make demands on the 4WD system and if it's not actually dropping any more, it'll probably be OK for a few days.
You did check it unladen? - self levelling system causes fluid level to drop temporarily when it compensates for a heavy load.
'08 Chrysler 300CRD (MB OM 642 engine)
'95 E220 estate
'89 230TE (R.I.P.)