I did mine recently. I used the small gear puller to put tension on the bottom of the stud then wacked the side of the casting with my small sledge. One side popped loose with the first wack. The other took a few. The key was the tension on the puller then the wack to shock the casting. The gear puller alone probably won't do it. Put the nut on loose so things stay put when it comes loose.
Steve
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