I have a 1999 gmc Yukon making a high pitch squeal over 20 mph. Very loud and can be heard with the windows up. Have new brakes on and wheels do not seem to have any play to them. Any suggestions

Is the squeal more pronounced during a turn? If so, that might indicate a wheel bearing. Any idea where the squeal is coming from (front, back, left, right)? Does the squeal go away if you apply the brakes lightly. Does it increase with RPM'* or with road speed. Maintain a steady speed of 30 MPH, listen for the loudness of the squeal, then drop down one or two gears while maintaining road speed at 30 MPH. Does the squeal increase or stay the same. Does the squeal get higher pitched as you speed up, or does it stay at the same pitch?

does it sound like a whistle or rubbing or cyclical sound. I had a noise like that once, was driving me bananas. One day sounded like the back, then the front, then the left then the right. I took a tape recorder ( yes a cassette one at that) and a micro phone with a long cord. I started recording. I would say left front and tape it to the front fender with painters tape, i would repeat the process at every wheel. then I listened to the tape. The left front was 3x louder than any other, it was the LF wheel bearing. of course it could be somewhere else..your noise that is.