I think the fill level is to the threads on the fill plug. Hard to overfill.

Those plugs are usually VERY tight -- often overtightened and/or locktited down.

I was warned not to fill the rear end on the 280 unless the weight of the car was on the wheels -- the axle tube on the left side will fill with oil if it is lower than the rear end, and hold more than a quart ---- serious over fill when the axle is level!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!