2004 Pontiac Grand Prix front end howling

What you're describing is exactly how front wheel bearings act when they're noisy. The looseness you mentioned has nothing to do with it. What you need to do is jack the front end off the ground and support the car on jack stands, run it in gear, then listen next to each bearing with a stethoscope. One will sound a little noisy and you'll think you found it, then the other one will be REALLY noisy and it will be obvious.

There are also some people who say they can feel the roughness by spinning the tire by hand while feeling the coil spring. I've never tried that yet so I can't say for sure if that works.

Be aware too that you can tell which bearing is noisy by steering one way or the other, as in changing lanes, with the pressed-in bearings, but with the bolt-on assembly like you have that can be misleading. The noise can sound like it's coming from the left side, it can become quiet when turning left, and STILL be the right one that's bad. Also, you won't hear it without a stethoscope while running it in gear jacked up. It's the vehicle's weight that is needed to make the noise occur.