Have you checked your rear driveshaft u-joints? Also would just check to make sure no fluid is leaking out the rear axle. Since the sound is directly proportional to your movement, would start look at whatever is moving/turning as the cause, starting with the easiest first. Not saying it isn't the tcase, but have never heard one squeal at all. Wouldn't hurt to double check the tcase fluid and see if the output shaft is leaking.
The beatings will continue until attitudes improve!
HID Quad bi-xenon + foglight retrofit