synthetic

replaced hubs w/ warns, replaced and repacked bearings.. could it be the preload(what is that?)

If I'm not mistaken, preloading is the big circular nut that you tighten to put the brake rotor assy onto the spindle, and how much that is torqued..its not very much FYI

Look in the FSM it tells you the whole procedure on how to do it. Don't screw with it without knowing what you are doing you can mess up the bearings.