Did you make sure to replace all the bearings? A missing bearing might account for some grittyness. Also look for pitting. You can do this by taking the bearings out cleaning the grease out then run a ball point pen along where the bearings were sitting (I think its called a bearing race?) if you feel alot of roughness then the hub could be pitted. This means that dirt and water got into the hub creating excess friction and this wore away little bits of the hub. What was the condition of the hub when you first took it apart? When you say gritty how bad is it? can it spin? After two years it might never spin like it was new but it might still work fine. This is just an educated guess I've only been wrenching for about a year so perhaps a more experienced person might know more.