Check your engine oil level also.
It seems hard to believe that that much ATF can be drawn up thru the small vacuum lines and getting burned but in theory it seems the best explanation for the ATF to escape without leaving a trace. If it's going into your coolant, unless your coolant was really low, you'd be overflowing with 4 extra quarts.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13