strange brake howling noise

Has anyone ever seen a suburban make a strange howl when the brakes are used at slow speed? Its not a squeak or grind and the pads and rotors are in good shape and they stop fine, but when pulling into a parking spot it often lets out a quick, loud howling noise.

Check your rear differential for axel seal leaks. When the fluid from the rear end leaks out on the shoes, it makes a howling sound when applying the brakes.
one posibility

Have you replaced them ever? How many miles? If done, did you machine the rotors?

If you replaced the pads with cheap ones, this is "normal", throw them away and buy good ones if you care about the noise. Make sure that any metal on metal contact points are greased (pads to guides in caliper especially), and apply "disc brake quiet" to the back of the pads.

Its coming from the front of the truck. The truck has 78,000mi on it and I replaced the pads and turned the rotors last year (cheap pads). The pads do squeak some, but that does'nt bother me. The howl I think is coming from the wheel cylinder area, or maybe even around the master cylinder. It does not sound like any noise I've heard from pads before, not a grinding or squeaking sound at all. If you've ever head the quick howl a city bus makes just as it comes to a stop, thats as close as I can describe it

Possibally a glaze buildup on the front rotors from the cheep pads. Is this mostly city driveing? Sometimes if you hit the highway and ride the brake for 10-20 secs. or so at 70, it will burn the glaze off. Not always but sometimes.
Yes I know that sound. that is the same sound of grease on the rear shoes

I agree with G.A.S had same problem with 98 3/4 ton truck you may not be able to see any leaks but it doesnt take much to make brakes howl like you described . I tought it was front brakes too but it was rear brakes with a bad rear end seal that created the noise

Has anyone ever seen a suburban make a strange howl when the brakes are used at slow speed? Its not a squeak or grind and the pads and rotors are in good shape and they stop fine, but when pulling into a parking spot it often lets out a quick, loud howling noise.

it is possible that the caliper is binding .... it also could be the pad lining fell off... so it would be best to inspect all of these items...