When upgrading the brakes/spindles/hubs on both my trucks I found that if you remove the wheel speed sensor you can at least see inside the hub. My first thought was adding a zerk in place of it would be doable on trucks without ABS, but I'm not sure if they grease would flow in and what would be needed for it to flow out. Or if the amount of grease would affect performance too.
Still haven't torn into any scrap hubs, since they are holding up my new frame for the time being.
