I bought a used GMC Sierra 1500 Extended cab 4x4 in August of 2008. The speedometer was working when I drove it off the lot but on the way home I passed a local police car and glanced down at my speedometer and it was sitting on zero. It worked from time to time after that but now it spends most of its time sitting at 70 m.p.h. while the vehicle is parked andsitting still. I understand that GM was sued because of this problem and I called GM in Detroit and the person I talked to informed me that only the 2003 and 2004 Chevies and GMCs had tho... read full review »