Hey all. I purchased a used 2012 V6 Terrain with 33,000 miles on it back in October. I have had it back to the GM dealer that sold it to me twice for what I describe a miss or maybe a Torque converter problem. When the vehicle reaches around 35-45 mph i get a shuttering affect like its either missing or the converter isn't locking up. Not sure what it is. Anyone else have this problem or maybe some suggerstions? The dealership replaced the coil and plug on the number 6 cylinder and they said it was fine but its not. Looking for answers or suggestions. Thanks