Park exists for exactly the same reason that you should ALWAYS leave a manual car parked in gear. There have been many many instances of cars rolling away when left parked on a hill secured by handbrake alone.

So what we have is, in fact, your "ideal gearbox", but with the advantage of being able to secure the car against (all too common) handbrake failure.

With any form of auto there is one disadvantage - the car can never "plan ahead" for an overtake or for engine braking. So a box with manual over-ride (with or without flappy paddles) is very useful.

Many decent auto's (again including Porsche PDK) never need to be driven in "manual" mode. You just leave them in auto and click for a downchange when you want one. Car defaults back to auto once your manoevre is completed. Best of all worlds!

Absolutely correct and exactly what mine does. If I want a lower gear in readiness for an overtake or hill descent I can just dial it in with the "down" paddle. Whichever gear I select means the car then only uses that gear or below (so dialing in "4" means the car uses 1,2,3,4). I'm then held in a lower gear ready to overtake. One long pull of the "up" paddle reverts the car to "D", full auto using all gears. Perfect.

There is a manual mode that holds which ever gear I've selected and doesn't change up or down from it (unless I reach the edge of the parameter of that gear or instigate "kickdown"), but I never use it as the box is always clever enough to invariably be in the correct gear anyway, other than in the circs above (such as preparing for an overtake).

Thankyou for doing this! There are so many that don't and is nothing more infuriating than being stuck in traffic, in the dark, for half an hour and having to endure this:

You're welcome! And I agree (but only at night).

As above, but on my box (6L80e - VXR8) I opted to leave the torque management switched on. It is there to protect the clutch packs between shifts and having burnt out and rebuilt several other (non electronic) boxes, I felt it was better to leave it as is. Here's a burnt pack out of a my old-school 700r4:


As some above posted, remapping the gearbox is sort of akin to fitting a shift-kit of old, but far more sophisticated and much easier. I detailed how I remapped my box here

I'm confused. Further up this thread we were told there is no clutch in a conventional auto, it was like two fans facing each other with one speeded up to turn the other.

Now we've got photos of burnt out auto clutches...

The torque convertor replaces the "clutch" found on a manual car. This is what allows the car to "idle" in gear, its just slipping - i.e. you are holding the other fan blade whilst the first one is blowing on it.

Inside the gearbox it still contains gears - or rather planetry gears - and each of these is selected using traditional wet clutches (like a motorbike clutch) or sometimes a band - which as the name suggests is just a piece of friction material around a drum (like a belt) that is clamped against it with a hydraulic piston.

Remember the Sturmey-Archer 3 speed on your push bike? - these are planetry gears, you could could change gear under full load - unlike Derailleur gears where really you need to back of the pedal a bit for a smooth change.

Its these clutches and belts that take a pounding during a shift and have to "hold" the torque once the gear has been selected. Too much torque during a shift results in slippage and wear (burning of the plates seen above).

Modern automatics (electronic based) employ "torque management (TM)" which consists of either retarding the ignition or even closing the throttle a bit to limit the amount of torque going through the gearbox during a shift - this prelongs clutch life (or allows them to cost save on components). The americans seem to love removing TM to get very sharp shifts that "chirp" the tyres - great for the drag strip but heavy on the entire drivetrain.

I believe this is why more and more manufacturers such as BMW are using automatics and torque management to limit drivetrain damage from torque of the big diesel engines, as its cheaper than fitting a strong manual box.


Dig around on youtube - there's a few decent videos (and plenty that will leave you just as confused)

Eliot.

That's very interesting, thanks chaps.

Although it brings me onto another question. Sorry.

When I manually down-shift (coming down a long hill, or maybe slowing at the end of a fast dual carriageway for a roundabout) for a little extra engine braking, years of driving manuals has me instinctively "lifting" the revs with a little pressure on the accelerator to help ease the engine up to higher revs for the lower gear.

A good idea on an auto, or better to let it deal with it itself?

Again it depends on what auto box you have, some are far more advanced than others and you should just leave them alone to get on with it.