Look at the bearing races. Look for pits, discoloration and scratches. If in doubt, replace them. I pack my rear axle bearings just like any other bearing. The rear end lube will wash and mix with the grease with no worries. Lube your seals on assembly too.
On the top of the pumpkin of the rear end, there should be a vent. It could be a hose, or a small metal cap type sleeve crimped to a nipple that will screw out. Make sure that is cleaned out real good too.
