I was wondering, I have a auto trans and if I put it to L gear and start going and when you lift off the pedal and floor it, it seems to go with a faster launch, does that do anything to the trans IF I switch gears from L to 2 and to Drive.
THX!!!!!

Do you mean will it do anything bad? No, it won't do anything bad.
Many people have tried this method at the track, what most found was letting the car shift itself provided the quickest times in the 1/4 mile.

So if I have it in L gear and am going like 15mph and ease off the gas and then floor it, for that push it wont hurt it, also when you let go after that it pulls to a hard stop, is that bad, and will it give me a good jump for a 15mph roll.
srry for all the Q"s

I doubt it would be any better than just cruising along at 15 then punching it. I wouldn't really recommend letting L(ow) gear slow your car to a stop though. Why put that much extra load on the tranny...it's not like there's a TorqueFlite, TH400, or C6 tranny in there.