Snapper Rider 337123BVE

I have a Snapper 331723BVE Rear Rider, and it's been taken back and forth to the shop for a problem with a leaking rt rear diffential. The grease keeps coming out of the end behind the rt rear tire, then spinning out onto the wheel. This empties the diffential case just as quick as , I put grease into it. How do, I get this junk machine to stop leaking this grease? Thanks Beauford,