I believe that there is another (unlikely) possibility here concerning the squealing of the rear tires.

If it squeals a lot on every slow speed turn the limited slip unit could be binding excessively.
This can be caused by having the wrong fluid/additive in the differential gear case.
Keep in mind that some chirping of the rear tires when turning is considered normal for a limited slip or posi-traction type rear end.

I guess determining what's abnormal is an issue here, a comparison ride in another GXP might be in order.


Good luck


Rickey