Is conventional automatic transmission the best choice?

[Alberto Michelatti]

I think that nowadays is out of our era that a human being has to think at what gear is better to shift to (an ECU can do this perfectly) and, moreover, having to move directly the clutch pedal that, for me, would haven't to exist. So I would like to explain because for me the conventional automatic transmission with hydraulic torque converter is the best choice:

1) since the birth of the automatic transmissions, there is no power flow interruption during gear shifting, like in the more quick Direct-Shift-Gerabox system of Audi/Volkswagen group; not even a robotized manual transmission like, for example, the BMW SMG (or Ferrari F1) can do this;

2) an ECU always knows exactly the input shaft rpm and the output shaft rpm, matching them perfectly just at the right moment (an human being never could do this so: in my opinion, this is quite impossible);

3) the engine can't never stall, shutting off by its own: with a manual transmission, when you take-off and don't apply sufficient throttle or release too fast the clutch pedal the engine can stall (very dangerous in the road traffic!); also when you have to do an emergency braking, maybe that for the panic you release the clutch pedal wrong and, as well, the engine can stall, leaving you with a much more less efficient braking system just in the wrong moment;

4) the automatic transmissions are electronically and perfectly self-protected against drivers mistakes and, moreover, there isn't to worry about clutch overheat or synchronizers wear;

5) for the life of car, there isn't to worry about the expensive clutch-disc substitution;

6) with a manual transmission, how many burning-wheels dragster-style starts can you do without the clutch overheats? With an automatic transmission, instead, you can do this for the times you want, endlessly;

7) with a manual transmission, when you are at a stop on a uphill, when you have to start you have to release very carefully the clutch pedal, risking to overheat it; with an automatic transmission, instead, you have just to apply trottle, regardless of the weather, grip, slope, car load and anything else;

8) due to the automatic transmission creep feature, at the stops on uphill it's like having a Subaru-like hill holder feature, because the car almost never go reverse;

9) with automatic transmissions there's less wear than on a clutch, and there's less wear on suspensions and crankshaft/lower engine because of lack of transmission snatchs;

10) due to the automatic transmission kick-down feature you can get speed very fast, pulling yourself out fastly from bad and dangerous traffic situations;

11) due to the up-to-3.0x torque multiplication feature of the torque converter, a car has more acceleration when you accelerate out of a stop. Moreover almost all automatic cars today have the torque converter lock-up clutch, that eliminates the slippage between the pump (input power, engine side) and the turbine (output power, transmission side) of the torque converter. This by-pass function is studied to improve fuel economy at constant speed.

12) for the ultimate, the comfort and satisfaction given by an automatic transmission in the city traffic, in my opinion, are really priceless; it's true that the fuel consumption in this condition is higher, but you also have a lot more acceleration and this is undoubtedly a safety factor;

If someone is interested in a very detailed description of an automatic transmission, here there is the explanation for the ZF "4HP18 Q/EH" one (using the Ravigneaux gear train arrangement): http://www.digest.net/alfa/FAQ/164/pb94/pb94-6.htm.

Here there is the description of the state-of-the-art 6 speed "TR-60SN" Aisin AW automatic transmission (using the Lepelletier gear train arrangement), fitted on the Porsche Cayenne and on the Volkswagen Touareg (as well as, for example, as on the Volkswagen New Beetle, Audi TT and Audi A3): 6speedautotranny.zip.

Alberto.

P.S.: please don't say this to anyone, but this is the untold reason why the automatic transmission is absolutely the best choice...

[Leighcm]

1.) What are your thoughts on CVTs?

2.) What are your thoughts on difficulty of repair for automatic vs. manual transmission?

[Alberto Michelatti]

1) It's true that there are also the Continuosly Variable Transmissions, but they are available only on very few makes, like for example Audi, with its Multitronic, Honda, Mini and Nissan. Furthermore the CVTs have the big problem that they are unable to manage high torque values. The top of the CVTs at the moment is the Multitronic transmission of the Audi A4/A6 3.2 V6 FSI, able to manage its 255 hp and 243 lb/ft of torque. However this is nothing campared to the 612 hp and 731 lb/ft of torque of the Mercedes-Benz SL 65 AMG Speedshift. Note that conventional automatic transmissions with torque converter are always used in heavy-duty situations, like for example on dragsters, bigfoots, dumpers and so on...

2) It's true that in case of breakdown you have to bring your car only to specialized technicians, but I think that modern conventional automatic transmissions are engineered to last "for life": in almost all cases now you don't even have to change the ATF! It's true that after many and many miles it comes the time that the automatic transmission have to be overhauled, but this happens usually after 200,000 miles or more, but at that time your car have to be scraped...

Alberto.

[Leighcm]

What about the CVTs on the Prius, RX400h, and GS450h? In the case of the GS450h especially, there's an extremely high power level: just the gasoline engine alone is 292hp and 267lb/ft tq, plus the electric motor. I believe combined peak torque is about 360 lb/ft.

[Alberto Michelatti]

What about the CVTs on the Prius, RX400h, and GS450h? Simply they don't have a CVT... They just have an epicyclic reducer and a metallic chain, all fitted in a transfer case located between the thermic Atkinson-cycle engine, the electric engine and the generator (for detailed description see http://www.cleangreencar.co.nz/page/prius-transmission and http://www.lexus.com/models/hybrid/perform...nnovations.html ).

However, in my opinion, the conventional automatic transmission with hydraulic torque converter remains the best.

Alberto.

[fidgits]

meh.

manual shifting is best ;)

[Leighcm]

meh.

manual shifting is best ;)

I feel the same way....love the Supra 6-speed Getrag.....

[89corolla]

I feel the same way....love the Supra 6-speed Getrag.....

It takes a driver to drive an old school car. These new cars are getting so refined that even a child can drive them fast. Active control suspensions will make everyone an expert.

[Leighcm]

Yes, I have to admit my GS350 IS a bit boring...but it's good for Las Vegas traffic jams! The Porsche with the 6 speed, on the other hand, is a fabulous car to drive, but absolute misery in any sort of traffic...

[B-R-T]

meh.

manual shifting is best ;)

you got that right

if you stall - get a bicycle ;) you'r not ready for a car :P

[B-R-T]

[6) with a manual transmission, how many burning-wheels dragster-style starts can you do without the clutch overheats? With an automatic transmission, instead, you can do this for the times you want, endlessly;

7) with a manual transmission, when you are at a stop on a uphill, when you have to start you have to release very carefully the clutch pedal, risking to overheat it; with an automatic transmission, instead, you have just to apply trottle, regardless of the weather, grip, slope, car load and anything else;

overheat clutch?! WTF?!

[B-R-T]

5) for the life of car, there isn't to worry about the expensive clutch-disc substitution;

yeah, right.. expensive.. ~100 bucks in 10 - 15 years.. VERY expensive... 8 bucks a year..

[B-R-T]

9) with automatic transmissions there's less wear than on a clutch, and there's less wear on suspensions and crankshaft/lower engine because of lack of transmission snatchs;

how does manual transmission adds more "wear to suspensions and crankshaft"?! are you &%#$* stupid or what? manual transmission is bad only for one thing. for a turbo without BOV. because, when throttle is closed when shifting gears the surge of compressed air smashes into turbocharger compressor blades, which in time causes shaft failure. but thats it. and if you have bov, you dont have this problem.

10) due to the automatic transmission kick-down feature you can get speed very fast, pulling yourself out fastly from bad and dangerous traffic situations;

Total bull$&@%...

[B-R-T]

11) due to the up-to-3.0x torque multiplication feature of the torque converter, a car has more acceleration when you accelerate out of a stop. Moreover almost all automatic cars today have the torque converter lock-up clutch, that eliminates the slippage between the pump (input power, engine side) and the turbine (output power, transmission side) of the torque converter. This by-pass function is studied to improve fuel economy at constant speed.

More acceleration? nope, wrong again ;)

ATs ar for dummies, who are to slow, to shift ;) And, obviosly, you are one of them :P

Thanks for a good dose of humor ;)

You are a funny guy good for you

[B-R-T]

Oh, BTW, did you know, that you cant tow a car with your beloved AT? ;) Even in "P". If your car brokes down a few miles from home, you cant call your friend to tow you with the rope. You have to get a truck with platform. If you tow it with a rope - your tranny's fried :P good luck with that

[Leighcm]

Oh, BTW, did you know, that you cant tow a car with your beloved AT? ;) Even in "P". If your car brokes down a few miles from home, you cant call your friend to tow you with the rope. You have to get a truck with platform. If you tow it with a rope - your tranny's fried :P good luck with that

1.) You don't have to get a towtruck with a platform for an automatic transmission vehicle. A normal tow truck will work with most automatic transmission vehicles; the exception being AWD/4WD vehicles. As long as the drive wheels are off the ground, you're good to go.

2.) You CAN tow an automatic transmission FWD/RWD for short distances at low speeds (under 35 mph or so) with all four wheels on the ground. I wouldn't recomend towing anything with a rope and a truck though...very dangerous.

3.) You're never going to want to tow ANYTHING with the transmission in "P". "N" works MUCH better for that sort of thing.

[B-R-T]

1.) You don't have to get a towtruck with a platform for an automatic transmission vehicle. A normal tow truck will work with most automatic transmission vehicles; the exception being AWD/4WD vehicles. As long as the drive wheels are off the ground, you're good to go.

2.) You CAN tow an automatic transmission FWD/RWD for short distances at low speeds (under 35 mph or so) with all four wheels on the ground. I wouldn't recomend towing anything with a rope and a truck though...very dangerous.

3.) You're never going to want to tow ANYTHING with the transmission in "P". "N" works MUCH better for that sort of thing.

my bad with that P, wrong letter

But N will not work either, because in N all planetary gears spins inside of the transmision and you still need at least runing engine. If you cant start your engine, you CAN'T tow even for a short distance! Because oil pressure is too low when engine is off (actually there are almost no pressure at all).

About a truck.. You missed my point. I wanten to say, that you HAVE to call for a truck. If you have manual transmission, you can call your friend. Which of those calls are cheaper?

It's not dangerous to tow with a rope.. If you know what you are doing. But when towing car even with manual transmision with engine off, the brakes will be almost useless because of absence of the vacuum inside intake manifold. Thats the only problem. Well, steering to, but thats not that important. Hell, I was driving my old '87 BMW without a power steering and I'm still alive :D I even made some good drifts <_< :P

Damn, I miss that car