ok on that ... I would guess your transfer case is bad... if 4wheel low works but not high.... Just an fyi you arent supposed to use 4wd on dry pavement. (you seem new to the 4wd thing so just a heads up)
Also be sure the PO wasnt an idiot and changed the gearing in one axle but not the other to match.... It happens... that makes the front wheels turn at a different speed than the rear.... mismatched size tires will also do this and thats why you want to use all 4 tires of the same size on a 4wd. otherwise it puts a lot of strain and force on things wearing or breaking them.