In June, I purchased a pre-owned 2008 Sub. LTZ with 36020 Miles. We have put appox. 5000 miles since purchased. In this time, two power locks have gone out, one door handle broke, and now the Service light indicates "Service four wheel drive". When turning, the front tires sounds like they are grinding the pavement and the front drive feels like the 4WD is engaged. Has anyone else experienced this or other problems? Did I buy a Lemon?