Replace the axle seals. The easiest way to put the hub back on without damaging the seal is to lighten the load by removing the brake drum, which you have already done. With the hub off, check for burrs on the axle housing, especially on the lip where the seal slides over. Before assembly use some grease on the seal and the lip on the axle, then carefully slide the hub on, holding it straight.
When replacing the seal you will see a spring inside the seal. This spring goes on the inside of the hub so it is filled with gear oil. That's how you know it's in correctly. Also, check the axle bearings, if you haven't already. If there are grooves from the old seal on the axle shaft, it's best to put on a ready-sleeve, or it will leak again.
Did you put in a new pinion seal? if not, it will probably leak, too. And Scott is right on the axle vent, if it's plugged up the vapor from warm gear lube will expand and blow out your new seals. I learned the hard way.
