My front end is moaning...

I've been noticing for the last month that the front end is moaning when I turn the wheel backing up or going forward... i thought at first that it sounded like it was low on power steering fluid... nope its showing plenty of fluid... when i was changing the oil and rear diff fluid this weekend i check out everything underneath and didn't see any signs of leaks... and there are no signs of leaks on the hoses up top... anybody have any ideas?