I'm trying to replace a rear pivot arm on a model 20332 Toro Recycler. After removing the wheel, retainer ring, pinion gear, and washers, I'm not sure how to get the pivot arm removed. The new part is threaded, so I'm assuming the old part is also. I soaked everything with PB Blaster, now what?

Before I strongarm this and cause damage, is there something

I am missing?