Not sure how many people know or not but the stepper motors on the dash clusters almost always fail causing the speedo to stop working or the various other quirks. The free fix is only for 03-10 and less than 80k miles and it does affect ALOT of models. consider this an fyi, look up your vehicle and see if yours is due as it cost a TON for a new one to replace. I did find a place to repair them rather reasonable in price but a free fix would have been ideal.
http://www.gmspeedometerrecall.com/