A transmission building friend (okay, so he won't admit to being my friend, so what!) of mine explained to me that, in the stock GM versions of automatic transmissions, second gear is the weakest one. But even so it takes a good bit of punishment for it to fail. I don't know if this translates across the board for all automatics of if it is GM specific. He builds drag racing automatic trannies. Mostly Turbohydromatic 350 and 400's.