I think , if the gears are engaged, wear and tear should not
happen, doesn't matter the car is moving or stop. The wear and tear
of the gear box only happens when the gears are seperated and cluch
in again.
Move from D to N means you seperate the gears and laster you move
from N to D you engage the gears again. The gear box suffers two
times unncecssary wear and tear in one traffic light. And the worst
case is you start the car immediately after you move the gear stick
back to D. (It more likely happens during the traffic light wait. )
Actually, your gears need some time to be fully engaged. Rush in
stepping the accelerator, will hurt your gear box very badly. So,
if believe in this theory, we should try not to move to N or P
unless there is no choice.
I won't worry about the stress on engine. It should be designed to
take such a low level stress.
