2005 T&C Touring 3.8

The rear driver-side wheel has started making a 'chirping' sound. Its loud enough to hear inside the van with the windows up, and gets pretty bad when you're at highway speeds. I have taken the wheel off, removed the caliper and rotor, everything looks OK. I spun the axle a few times by hand and didn't hear anything.

I cleaned the rotors before putting it all back together but the sound is still there. The pads look near new; very thick still. The e-brake shoes aren't great, but there's still some meat left on them. This is a mystery -- anyone have a similar problem?