I have been having an issue with my volt lately. When using the L with the regen braking or when the car has stopped and I go I have been hearing an audible click or snap sound. I spoke with my cousin who is a lead GM mechanic and he was able to diagnose the problem as one of two things without even seeing the car. Either the dog bone mount from the transmission to the frame is broken, which they are known to do, or I needed to take the tire off and retighten the axle nut with an impact wrench. He was correct because the dog bone looked fine so I went to tighten the axle nut and accidentally had the impact in reverse and it immediately started to turn off. After I tightened the nut, reinstalled the tire and put it back on the ground it no longer makes that sound. Just thought I'd pass that along to help out, its been driving me nuts for a little bit now.