I have 97 xplorer 500 and went thru the same thing. if changing the fluid did not work, you will want to take the hub assy apart. 1 remove brake caliper, 2 remove plastic cover on hub(catch the oil in something, it will run out)3 remove cotter pin and axle nut. whole assy slides off at this point. note order of bearings and all as you dissassemble. there is a clutch inside the hub assy that has rollers held on by a garter spring. on the back of this hub is a flat spacer that is the armature plate. check all parts for wear. replace armature plate if worn. check inner surface of hub for damage. if the strut hub seal sleeve is worn, the job gets a bit more complex and expensive. check out donwoodspolaris for exploded view schematics and part numbers. hit-the-gas on ebay has great prices on polaris parts. firstname.lastname@example.org
if you have and questions. good luck!