You remove the nut that's vertical, then if you're just replacing the mount, it's easiest to take the whole rear cover off and slide the entire thing down (after loosening the cover to mount nuts). If you're dropping the diff, then you loosen the driveshaft, axles, and the 4 long bolts holding the diff to the subframe, then remove the cover nuts and move the diff forward a bit, lower the mount straight down, then wiggle the diff out. Or take the cover off again. Thing is, removing the cover will be messy.