The sleeve you are talking about is NOT threaded it is just a spacer and provides a spot for the seal to ride against. It is designed so you can just slide the axle out once the nuts are removed. It has been my experience with these that they get rusted on tightly. I had to cut my last spacer and every bearing off with a diegrinder, before the axle would remove. I have always coated everything with antisieze during reassembly, it helps a bunch.
Josh
I had the RIGHT to remain silent, I didn't have the ability!