I'm currently rebuilding car. Yea I was racing in dusty condition and yea one of my outdrive bearings felt gritty - flushed it with brake cleaner, lubed with GT85 and it rolls like new - basically all schuey bearings work like this for me
Well, everyone have to consider that these bearings don't have rubber shields, so unless you're using grease, dirt will find way in. So just check it more often, clean and relube them again. I'm really using only GT85 for lubing all my bearings and they are nice free rolling.