This is a link to the best write up of changing fluids including the diff and transfer case I have seen from Mathews Volvo site so have a look at this for instructions and volumes:
https://www.matthewsvolvosite.com/fo...p?f=10&t=64335
And another ink that has some useful information on the topic.
https://www.matthewsvolvosite.com/fo...ic.php?t=45037