This past weekend I did just this. After removing the wheel and removing the fill plug, I lowered the jack until the vehicle was dead-level (69 cm to the top of each wheel well). I threaded my filler tube down through the engine bay and into the fill hole and added oil little-by-little until it started to ooze out. Then I zipped everything up.

The 1-2 shift is much better now. I don't have a good feel for how much extra oil I added, but it must have been less than 100 cc. Lesson learned: 2.75 L is not enough oil, no matter what the book says.

Now I'm going to have to open the rear diff up again and do the same thing, since I filled that up with exactly what the book said (1.9 L).

 

The differential fluid is filled in the same manner, although getting the correct level is more difficult due to the location of the filler hole and the surrounding bodywork.