Hello Sylvain,
See
http://www.mapleleafup.net/vehicles/.../fordspec.html under "Lubrication Capacity": Transfer Case - 2 pts. for all models.
A US Pint (Liquid) equals to 0.473 liter. so 2 pints is 0.946 liter. Your 2.8 liter equals to the 5 pints quoted by Niels. If it spills out at the vents it clearly is too much.
Hanno