Let me start by saying that I have never owned an auto tranny car. Last week, I was driving around in "D", which is pretty rare. I had my hand resting on the shifter and accidentally knocked it into "N"... To be safe, I came to a complete stop, then put it back into "D". My question is, what would have happened had I put it back into "D" while the car was still moving? Would my transmission have dropped out from under the car? Something tells me that car manufacturers wouldn't allow this to happen though. TIA

 

the car would go find the appropriate gear and shift into it, and no - you're tranny would not fall from underneath the car

 

Another question. WHat about when on a full stop and you rev the engine hard and put the transmission into drive from neutral? How will that affect the transmission? In the long run?

 

I wouldn't recommend that. Puts major shock on the drive train. I also wouldn't suggest shifting from D to R while moving. Puts major parts of your trans on the concrete.

If you want to power launch you can put it in D while pressing the brake and revving to 2k or so (just before the rear wheels spin against the brakes). Then release the brake and floor it.