With the "ecco" alloy wheels, the center cover that has 'Jeep' on it will sqeak or chirp. You can hear it when driving slowly.
The disc brake pads on an XJ does not have a squeak indicator. The pads could chirp but will stop when you press on the brake pedal a little bit.
Wheel bearings don't chirp usually, they knd of growl.
Which end, front or back?