:help: My GSD was a big time car chaser as a pup. I would tell him no over and over and he quit doing it for the most part. But when we are out on a walk, and not very often does he do this, but he will occasionally regress to his car chasing ways and lunge for a car suddenly, and since he is a big boy now, he nearly takes my arm off. He walks great on the leash, but he catches me totally off guard, because he will stop doing it for a long time and then BAM-he does it again. I welcome all ideas on how to get him to permanently stop this!