I think the 706 is like my 806. If so, there are at least 3 plugs- all of them are on the centerline of the axle- one on each of the axle housings right next to the main housing and one on the center of the main housing. All 3 need to be pulled to get the old oil out, unless it has had the hole drilled in the axle housings to let oil drain back to the center. If you have a "swinging" drawbar, you may need to pull it out to get at the center housing plug. I've pulled mine out for that purpose, at least. All 3 castings fill as one. IIRC there is also a plug to drain the PTO unit.
It may take a couple filter changes to get all the Jello out. The Jello is just Hy-tran that has absorbed as much water as it can. I had to change the filter 2 or 3 times when I first got my 806 going- and that was after changing the hy-tran! -Andy