My goodman gmnt100-4b squeals when running. It sounds like it is coming from the squirell cage. Thinking I had a bad motor I replaced it along with the capacitor, but the squeal is still there. I have pulled out the squirrel cage and checked that the blower rotates freely which it does. The squeal will immediately stop when the power to the motor is cut. The blower will wind down with no noise. The blower rotates freely and does not appear to be out of balance. There are no other obstructions in the cage. What else could be causing the noise?

Make sure the side clearance is correct. When the motor starts, the thrust pushes the cage out and it could be just lightly touching the plenum. Since you replaced the motor, I see no other reason. Are you sure it is a squeal and not a wind or air noise from a return or supply?