Unusual

by the pan do you mean sump guard? Normally if you over fill a 280 it blows it out of the rear crank seal. Undo the white plastic drain bung in the bell housing and see if its coming out of there. This drain bung is to let water out. If you do not intend off roading I would be inclined to leave this out as it lets any excess oil to drain and not get thrown into stater motor. Look at your stater motor at the solenoid, is it dripping out of the bottom of there.

NOTE. There was a modification to the dipstick on the early 280 auto as the dipsticks were to lshort and where giving a false reading to they were being overfilled and blowing the rear crank seal. Always use 20w/50 oil and only fill to 3/4 full.