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?
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)