Squealing noise during slow speeds

[xbreedjr]

My 2005 Expedition has been making a new noise lately. When driving at lower speeds (under 20 mph) after driving for about five minutes or so, you’ll notice a constant squealing-type of noise that seems to be coming from under the car. It’s got new brakes and pressing the brake doesn’t alter the noise at all, also just had driveshaft u joints replaced 2k miles ago and trans rebuilt. Also doesn’t change when the wheel is turned/straight. Wondering if it’s maybe a problem with the diff or 4wd vacuum lines?

 

[whtbronco]

With new rear brakes it could very well be your parking brake. When it's squeaking just set the parking brake 1-3 clicks to see and then release it soon after of course.

 

[texasscot]

For squealing noises I’m immediately drawn to serpentine belt and pulleys, may be worth ruling out.

 

[GaryH]

Check the serpentine belt and all of the idler pulleys. I don't think the belt would squeal unless it's very loose, but the idler pulleys can and do wear out. Also check the belt tensioner.

 

[BlackCoffee]

I am thinking belts as well, or maybe the tensioner. Far fetched idea, but older cars you find a lot more hard to diagnose problems. May want to check the harmonic balancer. The rubber may have deteriorated a bit, it will slip like the serpentine belt before it fails.