I need to get the back wheel off my JD Sabre mower. It looks like there is a shear pin that is holding it on after I get the big snap ring off. How do I get the pin out?

There should be a plastic cap covering a spring clip over the end of the axle.
Once the clip is off the wheel should slide right off the axle.
There is a groove in the wheel that matches the long key in the axle. Do not remove this key. It is a pain to put back.
Use a rubber mallet from the back side. Jack up the back. While slowly turning the wheel, tap the wheel out from the inside. It should release. Usually this is not necessary.
You may have rust on the axle, if it is severely weathered.
GL
DNO

Worked at a John Deere dealership 15 years a go and the wheel issue was a nightmare. We would heat RED hot and douse with cold water this would cause it to contract and loosen.

Hope the rubber mallet works.

Don