Getting NSS off

I've read the threads, and my situation is a bit different in that the actual body of the switch separated from the base of the wiper arm. In other words, the switch itself is off, but the part that presses onto the shaft on the trans. is still there.

My question is, how hard can I hit a chisel on the split lobes of that threaded wiper-arm body without damaging the shaft entering the transmission? A chisel is the only way I can think of to get the bastard off. I'd tried every method I've read about before just breaking the damn thing.

Thanks for any help.

You must be gentle with it. You might just need to find a puller or something like that to get it off. Maybe a battery post puller or a two jawed small puller. Good Luck!