I will soon start my studying for a driver's license and I'm a bit curious about the behavior of the automatic gear.
I know that some modern automatic cars are equipped with a DSG gear while most are equipped with "standard" gear which is made of "complex hydraulic systems".
I felt that when a bus (probably not equipped with DSG) put the gear into D mode from N while still pressing the brakes, the bus started shaking and produce louder engine sounds. I assume that what is happening is that the clutch (or whatever) went into the friction point where the engine isn't completely connected to the wheels, but still transfer power (I took physics, I know the difference between static and dynamic friction) to the wheels, therefore the sound and vibrations.
In the DSG car I haven't felt it. I also know its a more efficient gear. Is it smart enough to completely "press the clutch" to separate the engine from wheels and only attach when the brakes is not pressed, or am I wrong? Is my guess about "standard" gear correct?