Wife was driving the Tahoe around a corner ~15 mph (slow on the street), then she heard a big metalic BOOM. The revs rose and she just started to coast. She tried all forward and reverse gears - nothing.
It turns out the sprag that grabs the inner and outer races of the transmission became unattached. The dealer rebulit the transmission under warranty
. It seems like this is a common problem for the 4L60E - maybe a Friday build
? I would have paid to upgrade to Monster parts since they were tearing into it, but I could not have the truck down waiting for parts and install. It was up and running the next day.