Following are the different types of Automatic transmissions & a little of how they work - 1) Automatic transmission
This is the one 350z was talking about.
It has *Park(P) *Reverse(R) *Neutral(N) *Drive(D) *Second(S or 2).
This transmission does not have a clutch.I am not talking about the clutch pedal here,what i mean is there is no clutch plate in the transmission.It uses torque converter instead.Now the gears are changed by hydraulics depending on the oil pressure exerted inside the gearbox
Hence - The shifts are slow,mileage is less & car is slow compared to Manual Transmission & other automatic transmission.
This type of gearbox is found on i10,verna,etc 2) Automatic with paddle shifters
(Triptronic/semi automatic) -
These are same as automatic transmission(above) & have (P)(R)(N)(D)(2) with a additional (S) mode in which every gear is held until redline before shifting to next gear irrespective of what is the oil pressure in the gearbox
Now all they have done is added a small micro chip & paddle shifters to this setup so that you can change to next gear when you press the paddle irrespective of the oil pressure inside the gearbox
Even this is slower when compared to manual transmission,but faster than the Automatic transmission.
Cars which have this gearbox is the civic automatic.
Now there are some manufacturers whho have this Triptronic gearbox but they don't give paddle shifters on the steering wheel. Instead they give this + & - ing of gears on the gear knob. You have to push the gear knob in a certain slot (this is when the gearbox goes in semi automatic mode) & the just press the gear knob in front to Up shift & at back to Down shift.
This type of Automatic transmission,where the gear knob itself is the shifter instead of paddles on steering wheel is found on cars like Sonata diesel,etc. 3) DSG Transmission with triptroni gearbox
Now this is the fastest gearbox,faster than the Manual transmission.It changes gears with in seconds.This is the tech used in F1 cars. This gearbox has two clutch plates.
This gearbox can be used as normal Automatic Transmission with (P)(R)(N)(D)(2) & with Paddle shifters in S mode.
But these paddle shifters are far more faster than the normal triptronic gearbox just because these have two clutches.When you are in 3rd gear the next clutch plate automatically mates with 2nd or 4th gear depending on engine load & hence the shifts are super fast,with in milli seconds.
This type of gearboxes are found on Laura,Superb,etc.
Hope all the doubts are cleared now