After having a GM rebuilt engine installed at 120,000, now the vehicle is shuddering when lightly accelerating. It feels like the front wheels are rolling over railroad tracks. I'm not sure how much a repair is going to be. If your vehicle is shuddering when lightly accelerating, do not let the dealership lead you astray and try out all the other possibilities like coils, or faulty ignition. From what I've read online, the reprogramming of the transmission is not an effective long lasting repair.