What are you torquing the spindle nut to? Should be 74 ft-lbs. Some manuals give the same spec as the front, 129 ft-lbs, which is wrong.
How are you packing the bearings? Are you removing the outer bearing seals and just smearing some grease in? Grease compatibility could be an issue, and you really shouldn't mix greases unless you know they are the same type or are compatible.