High pitched whistle

My wife's '01 Sport Trac is making a shrill whistling noise. It's coming
from the right side and only when the vehicle is rolling. It's also very
intermittent. We've never heard it at hwy speeds and sporadically in stop
and go traffic. Applying the brakes makes no difference in the sound, nor
does turning, either direction. Anyone got any ideas what the problem could
be?

Dave

Have you checked the brake pads all around. The rivets on the brake
pads may be touching the rotor. This happened on our 1996 explorer.
You would probably see grooves worn in your rotor, if this is the case.
Could be on the back side of the rotor as well. I our case, it was
the left rear rotor. The brake pad had partly crumbled away and wore
down so that the riviets were scraping against the rotor. It was a
very high pitched, ear piercing squeal/whistle. At first I thought it
was the wheel bearings but they seem to be fine. Hope this helps.

Byron