mine also did that, but mine went from humming to grinding sound. so i had the wheel bearings changed
1999 ranger 4x4 supercab, 4.0L
-3 inch PA body lift
-16 inch pro comp alloys
-33x11.50 BFG all terrain
-Go Rihno roll bar with 4 KC Daylighter lights
-weston bull bar
-air box mod, tightend throttle cable.