If you have air, use an air chisel as it will make the job a lot less frustrating. The goop used to seal the third to the rear housing is some bad ass stuff. The air makes the hammer/chisel work a piece of cake. Also remember to keep a couple three bolts holding the third too the housing in, keep an eighth of an inch or so clearance from the bolt head to the thirdmember. This will keep the third from taking off when you do finally break it free.
And please do not beat on the flange, not a good idea.