This should be illegal to sell a defective car, people have love one's in their car and society is at large. I was driving my son and lady home on the New York City Express Way (BQE) and the car seemed to over power, did a jerk and suddenly stopped with thousands of cars behind me. I had to use all my skills to prevent myself and loved one's from getting hurt. I spoke with some people about this and they knew it had to do the power train. Therefore, I purchased a new power train relay, but that has not helped. GMC is at fault and it's not worth the money of selling a car. How long can a car be on the road before it's enough. My list with this car goes on and on overall mechanic can not fix the problems.