its tough on any wheel bearings when soaked in muddy water constantly. Im not 100% on what kind is in the ranger now but greasable bearing would be ideal... if they even make them.
But they do make better quality sealed bearings either way. Also greaseable ball joints will save a lot of trouble also... when your able to grease a bearing or joint you can push out contaminants
Amen to that, if your driving in wet/muddy conditions and then grease a bearing you will be amazed at how much water and dirt the grease pushes out.