I have a 2002 FX4 4x4 with 42,000 on it. I have recently noticed a pulsating sound when I brake..........woowoowoowoowoo or humming like a truck with thornbirds or something, but it only happens when I hit the brakes. Is this my breaks rotors or what. My tires only have 1/8th inch of tread on them so I was thinking it could be my tires but it only makes the noise when I brake. Anybody have any ideas, I would greatly appreciate some input.
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42,000 miles, better get em checked out.

 

you say "pulsating sound". If it is a pulsating feeling from the brake pedal (not a sound) then it is very likely your brake rotors. With the sound you describe, i'd suspect bad brake pads, possibly bad rotors, wheel bearings or loose calipers. i dont know much about 4X4's though so maybe something about the 4X4 setup is contributing to the noise.

 

I do no not feel any vibration through the pedal, it seems like it only does it on hard braking, nobody else has had this problem, I am thinking brakes and rotors also.

 

Without a pulsating pedal I would say it is tire noise. Not all that uncommon

 

Like Pestco1 said, I think its tire noise, especially if its loudest between 25-40 due to the weight shift to the front while braking. Get the brakes checked anyway!

 

Yours could be a whole lot of things: Tire noise, wheel bearings, or brakes all come to mind. I'd put my money on the brakes as mine did that exact same thing for about 4 months. Turned out to be the lower slide pin on the driver's side froze up, causing the inside pad to wear out prematurely. Got my truck a brake job for Christmas.

-Joe