While I was driving the vehicle started jerking and not changing gears. Several times it almost caused an accident with me and my son in the car. I turned the car on/off and restarted it at the red light, the exact same thing happens. Lucky a GMC dealer ship was near by. I was able to get there still jerking and not changing gears. No warning signs appear during this whole time. No prior issues with the transmission. Once I made it to the dealship then engine like came on. Really now! The dealer checked vehicle and stated the transmission is gone out. I was flabbergasted, almost $10,000 had to be replaced.