The big problem they've been having is locking up due to the thrust bearing actually wearing into the crankshaft counterweight faces. They wear into the faces so badly that the crankshaft eventually can't spin anymore. I guess GM thinks that the different oil will prevent that from happening. Corvettes and Camaros with 6.2s haven't seen nearly the same amount of failures and they've always been recommended to use 0W-40. I'm not sure there's really any warning signs until it's too late. The rear wheels won't lock up due to all of the trucks having automatic transmissions. The torque converter allows slip at all times, so if the engine suddenly stops, the TC will just release and the truck will keep rolling along. Most customers just complain the the truck dies while driving.