How did you check the fluid, engine cold and off, at operating temp and in gear, or some other method?
If you checked it cold, then the fluid should be about 10mm below the lower line if full. At operating temp, in gear and parking brake on, it should be at the upper line.
And if you need to add, Dextron III will be fine. Just be sure not to overfill.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.