In November 2008 I bought a Silverado 4x4 to replace my stolen 2007 Avalanche 4x4. Since November I have had the truck in the shop on 2 separate occasions, once the shop basically calling me a lier because they didn't find anything. 2nd time I took a picture of the 4x4 light and took it to them again. This time they said that they found a POO sensor bad. About 4 weeks after they should have ordered the part, I call them and they had not ordered the part, but then called back and said it would be there in a week. Having to work, i didn't have time to take my truck in. Regular Maintenance Oil change, they found that the differential fluid is white / milky, oil was coal black and transmission oil was considerably low. Prior to this, the 4x4 light would change from 4x2 to 4x4 high / low while driving and at times, actually kicking in the 4x4. Planned to take it to the dealer again for the 4x4 sensor and other issues but while my wife was driving it, the 4x4 appears to have kicked in and caused her to go into a ditch because it was unexpected. Up to $12000 in damage as of right now and still going. Anybody have this issue with GM? I wonder what my options would be right now? Body shop is also going to be looking at the 4x4 and go from there.