So I'm wondering what everyone thinks about this, growing up my father taught me to drive and I allways remember with the few autos we owned him allways telling me to shift to neutral while sitting at lights or traffic. He told me that just holding the brake puts undue stress on the trany ie the brakes holding the transmision from working. So I wonder which is worse the more frequent shifting D to N or holding the transmision still while it still wants to move, just to clarify what I mean is when on flat ground and with no brake the car slowly moves tranny doing what it's supose to where holding the brake is keeping the trany from doing what it should... move the car. I'm very interested in what people think about this was he correct or what?

 

well always trust the savy ones... your father is one of them

 

Not true, when idling the tranny moves to pseudo D (internal N) even though the stick shows D.
The trannies are intelligent when you take your leg off the brakes ABS sensor/speed sensor feedback will get it from internal N->D.

 

Ok so why does the idle change when I manualy shift to neutral also the brake pedal gets softer not that I dont believe you just curious

 

When I am at intersections that make me sit for 3-5 min (very common in Bay Area), I move the stick to N and turn the car off. This not only saves gas but gives my feet a break from holdling the brake pedal down.

You may ask me why N and not P. If I was late to jump when the light changes to green, then the rear end collision won't shot my park gear teeth..

 

while in D holding the brakes, the tranny is actually in gear, but unlike manual tranny, the torque converter acts like a clutch, which uses ATF to send torque, so it still sends torque to the wheels but not big enough to against brakes.
in hot days, torque converter would put extra heat on tranny if sitting in traffic for a long time.

 

Jime mentioned that at the track what caused the highest tranny temps was loading up the car, granted that's worse than just being in D at idle, but still.