While the TrueTrac will help with your RWD launch, it won't be a perfect alternative/replacement for a 4-High launch. Having all four tires pulling your truck forward at launch will give you a better 60-ft time regardless of what rear differential you have. You are correct in that 4H launches aren't great for your transfer case, and the TrueTrac will help you if you switch over to RWD-only launches, but it's not the perfect replacement. As for turning, the thing you have to keep in mind is that the TrueTrac is an LSD, so it functions as an open differential during normal driving when the torque differential between the two rear wheels is low. Once that torque differential reaches a certain threshold (i.e. losing traction), the diff locks up and feeds power to both wheels until that differential torque falls.