I'd suggest disassembling it and inspect and inspect all metal parts for wear or breakage. Reassemble with new "O" rings, seal and gasket. The "O" rings you could buy at a hardware store.
Here's a link to a seal....
https://www.ebay.com/itm/SKF-6903-Tr...IAAOSwZxZeds-d
or here....
https://www.partstree.com/parts/cub-cadet-721-3011/