GM working on 7-/8-speed transmissions

[Drew Dowdell]

My car has a DOHC V8, it is better than any pushrod, much quieter and smoother. The CTS is an entry level car, it is $32,000, that is less than a C-class or 3-series base model. $42,000 is where luxury tax starts. Cadillac's dimensions are just all wrong. $50,000 is middle luxury, an E-class is $51,000 base. An S-class is $89,000 base, although many other upper end sedans start in the $75-80k range. Cadillac's most expensive sedan bases at $43,000. There is nothing wrong with the CTS's interior when compared to other entry level cars like the TL, G35, etc. And their V8 model will be a pushrod, Mercedes and BMW drivers are not going to trade their car in on. Cadillac is hoping that a Charger or Mustang driver that got a pay raise will come buy their loud, rough, pushrod, 1970s muscle car engine and think it is a fitting for a luxury car.

I admit I hate pushrods, I owned one, I'd never buy one again. Luckily for me there are 10 other luxury brands that offer all DOHC, so not like I'll have a hard time finding a car.

Is it Cadillac's sizing that is wrong or Cadillac's pricing that is wrong?

BMW has already proven that you can ask $42k for a 230hp AWD midsize car with "leatherette". Cadillac is probably leaving money on the table.

[pow]

Oh for f@#k sake! The TL has the TSX under it, A4 has A3, G35 is on the small end of the midsize scale and the coupe is listed as a compact.

You wouldn't compare the Lucerne to the 3 series even though they share a similar price range, why does the CTS get lumped in with the 3-series when it's dimensions and equipment meet or exceed the 5-series for most of the model range? The CTS is only a 3-series competitor because the 5er is so f@#king expensive.

If Cadillac priced the CTS in alignment with the 5-series and equipped it with those 20-way power seats which are such a deal breaker for some, you'd be screaming bloody murder!

Cadillac can't win with you people because you sneer at them for offering a 5er at 3er price or you sneer at them when their car priced the same as a 3er doesn't handle as well as the BMW because it's the size of a 5er. Jesus tap dancing christ what do you want from them?!

Woah, woah, woah, I never said anything against the CTS. I think it's a fabulous car, and no one has sneered against it. Even Edmunds realizes that the CTS offers more style and size than the 3er in exchange for handling, and that's a perfectly fine compromise. Every car offers something unique to the segment.

The 5er is priced in line with every other mid-lux sedan: STS, E-class, A6, GS, M, S-type, and S80. All of them offer luxury-oriented V8 engines (non-M, V, AMG, RS, F, R), greater sophistication, and mid-lux features like adaptive cruise control.

Again, I'm not "complaining" about the CTS. But there's more to a segment than dimensions alone.

[pow]

Is it Cadillac's sizing that is wrong or Cadillac's pricing that is wrong?

BMW has already proven that you can ask $42k for a 230hp AWD midsize car with "leatherette". Cadillac is probably leaving money on the table.

There's nothing wrong with either, IMO. The CTS is priced well competitively, and who cares if it's in the larger end of its segment. The end result is a sleeker, more coupe-like design anyway.

[VenSeattle]

The CTS is an entry level car, it is $32,000, that is less than a C-class or 3-series base model.

Mercedes Benz C300 Base price is $31,975

Oh... and it must get lonely in your bubble.

[cletus8269]

My car has a DOHC V8, it is better than any pushrod, much quieter and smoother. The CTS is an entry level car, it is $32,000, that is less than a C-class or 3-series base model. $42,000 is where luxury tax starts. Cadillac's dimensions are just all wrong. $50,000 is middle luxury, an E-class is $51,000 base. An S-class is $89,000 base, although many other upper end sedans start in the $75-80k range. Cadillac's most expensive sedan bases at $43,000. There is nothing wrong with the CTS's interior when compared to other entry level cars like the TL, G35, etc. And their V8 model will be a pushrod, Mercedes and BMW drivers are not going to trade their car in on. Cadillac is hoping that a Charger or Mustang driver that got a pay raise will come buy their loud, rough, pushrod, 1970s muscle car engine and think it is a fitting for a luxury car.

I admit I hate pushrods, I owned one, I'd never buy one again. Luckily for me there are 10 other luxury brands that offer all DOHC, so not like I'll have a hard time finding a car.

yeah youd never see a bmw owner trade say an 04 545iM in on a pushrod v8 like an 07 corvette coupe.... they just dont do that... and yeat i have a contractor friend thats in the process of doing just that. nevermind its a vette... its a PUSHROD bum bum buuuuuuuuuuum!!!!

what does any of this have to do with a transmission anyway?

[Z-06]

My car has a DOHC V8, it is better than any pushrod, much quieter and smoother. The CTS is an entry level car, it is $32,000, that is less than a C-class or 3-series base model. $42,000 is where luxury tax starts. Cadillac's dimensions are just all wrong. $50,000 is middle luxury, an E-class is $51,000 base. An S-class is $89,000 base, although many other upper end sedans start in the $75-80k range. Cadillac's most expensive sedan bases at $43,000. There is nothing wrong with the CTS's interior when compared to other entry level cars like the TL, G35, etc. And their V8 model will be a pushrod, Mercedes and BMW drivers are not going to trade their car in on. Cadillac is hoping that a Charger or Mustang driver that got a pay raise will come buy their loud, rough, pushrod, 1970s muscle car engine and think it is a fitting for a luxury car.

I admit I hate pushrods, I owned one, I'd never buy one again. Luckily for me there are 10 other luxury brands that offer all DOHC, so not like I'll have a hard time finding a car.

Now in the discussions of TRANSMISSIONS, where does PUSHROD comes into picture?

Here is a therapy lesson for you, when you go to sleep tonight say

OHV ENGINES ARE GOOD

fifteen times.

[smk4565]

yeah youd never see a bmw owner trade say an 04 545iM in on a pushrod v8 like an 07 corvette coupe.... they just dont do that... and yeat i have a contractor friend thats in the process of doing just that. nevermind its a vette... its a PUSHROD bum bum buuuuuuuuuuum!!!!

what does any of this have to do with a transmission anyway?

Corvette is a different kind of car. I was talking about people trading in 5-series for STS or CTS, it isn't going to happen with a lot of frequency. That is why BMW sales go up every year 5-10% and Cadillac sales have been stagnant or falling lately. Cadillac is still at a similar sales level as they were in the early 90s, when Lexus, Mercedes and BMW were hardly making a big impact, now those brands all sell far more than Cadillac. Cadillac's average buyer is still over 60, along with Lincoln, Buick and Jaguar. They need new products, fast.

And while GM is studying a 7 speed transmission, Mercedes is is in their third year actually making one.

[Drew Dowdell]

Corvette is a different kind of car. I was talking about people trading in 5-series for STS or CTS, it isn't going to happen with a lot of frequency. That is why BMW sales go up every year 5-10% and Cadillac sales have been stagnant or falling lately. Cadillac is still at a similar sales level as they were in the early 90s, when Lexus, Mercedes and BMW were hardly making a big impact, now those brands all sell far more than Cadillac. Cadillac's average buyer is still over 60, along with Lincoln, Buick and Jaguar. They need new products, fast.

And while GM is studying a 7 speed transmission, Mercedes is is in their third year actually making one.

I look forward to seeing conquest rates for the CTS next may.

[SuperSport623]

maybe i'm behind the times, but the last time i thought about buying a car i didnt put into factor it wasnt a 20 way power seat... but i dont care about power this and that because i see that as 20 different ways that seat can stop working. pillow in the seat? 7.1 surround? thats things i would look for in a living room not my car. i am probably speaking for myself and i know these are 45-55K dollar cars but i know that when it comes to me... who gives a $h*t about a seat.

Couldnt have said it better... i must have an old soul... i am perfectly happy with my 36 year old car with manual steering, two way adjustable manual bench seat, no ac, 3 speed auto, manual windows, manual locks etc etc...

screw new cars, im sticking to vintage iron

[cletus8269]

Corvette is a different kind of car. I was talking about people trading in 5-series for STS or CTS, it isn't going to happen with a lot of frequency. That is why BMW sales go up every year 5-10% and Cadillac sales have been stagnant or falling lately. Cadillac is still at a similar sales level as they were in the early 90s, when Lexus, Mercedes and BMW were hardly making a big impact, now those brands all sell far more than Cadillac. Cadillac's average buyer is still over 60, along with Lincoln, Buick and Jaguar. They need new products, fast.

And while GM is studying a 7 speed transmission, Mercedes is is in their third year actually making one.

but my point is they want a noisy outdated pushrod over the beamer... nevermind the fact its a vette. earlier the rant was about pushrods and how bad they are... remember?

Edited October 19, 2007 by cletus8269

[smk4565]

but my point is they want a noisy outdated pushrod over the beamer... nevermind the fact its a vette. earlier the rant was about pushrods and how bad they are... remember?

The Vette is noisy, but so are most other sports cars. So it doesn't hurt the Vette that much. Put that noisy engine in a Cadillac, compared to the quiet, smooth Lexus, BMW, and Benz models and the Cadillac doesn't match up as well. It is the same reason the Malibu is all DOHC now, they can't compete with the Camry with a pushrod and 4-speed auto. Pushrod V8s aren't as bad as pushrod V6s because the V8 is naturally smoother, and in a sports car or pick up truck you can get away with it still. And for a pickup, it is alsmost better because of low end power, and refinement not mattering as much, but they have no place in luxury cars, and I know Bentley has one, but they are Bentley.

[Flybrian]

The Vette is noisy, but so are most other sports cars. So it doesn't hurt the Vette that much. Put that noisy engine in a Cadillac, compared to the quiet, smooth Lexus, BMW, and Benz models and the Cadillac doesn't match up as well. It is the same reason the Malibu is all DOHC now, they can't compete with the Camry with a pushrod and 4-speed auto. Pushrod V8s aren't as bad as pushrod V6s because the V8 is naturally smoother, and in a sports car or pick up truck you can get away with it still. And for a pickup, it is alsmost better because of low end power, and refinement not mattering as much, but they have no place in luxury cars, and I know Bentley has one, but they are Bentley.

I'll counter with...

A) Lexus engines aren't 'quiet, smooth' in a suave sense; they're hauntingly silent. I don't want a car whose powertrain I can't hear.

B) I'll put a Hydromatic 4-speed next to anything for smoothness and shift quality. I'm not saying I wouldn't mind an extra gear above 'four,' but in both the 4.0l Aurora and 3800 II s/c Bonnie, the transmission is beyond reproach, 120-130k miles notwithstanding. People look at 5 > 4 more than any real measure of transmission quality you'll have to endure for the life of a vehicle.

[Drew Dowdell]

Lexus engines are wrapped in enough sound insulation to make the Pink Panther jealous. Throw in motor mounts made of marshmellows <or active motor mounts> and yea... it'll be smoother.

Guess what, the 3800 in the Lucerne is smooth and quiet to drive too and LeSabres and Bonnevilles were some of the first cars that came with an interlock so that you couldn't engage the starter while the engine was running because so many people couldn't tell when it was on.

[thegriffon]

The Vette is noisy, but so are most other sports cars. So it doesn't hurt the Vette that much. Put that noisy engine in a Cadillac, compared to the quiet, smooth Lexus, BMW, and Benz models and the Cadillac doesn't match up as well. It is the same reason the Malibu is all DOHC now, they can't compete with the Camry with a pushrod and 4-speed auto. Pushrod V8s aren't as bad as pushrod V6s because the V8 is naturally smoother, and in a sports car or pick up truck you can get away with it still. And for a pickup, it is almost better because of low end power, and refinement not mattering as much, but they have no place in luxury cars, and I know Bentley has one, but they are Bentley.

Neither a lack of smoothness nor low-end power are inherent to the cam-in-block pushrod design. Both are down to the specifics of the actual application. GM has a tendency to favor low-end power (the atlas DOHC truck engines have even lower torque peaks than the pushrod engines). Pushrods are cheaper, and more compact, at least in V-engines. OHC engines however allow an easier implementation of multivalve intake and exhaust systems, which can improve performance at high rpms, and allow separate phasing of the intake and exhaust cams more simply than with a single-cam design (although Chrysler does use independent intake phasing in the pushrod Viper V10). Once you decide you need a multi-cam design there is really no great advantage to using a pushrods unless packaging is critical factor. Honda however has used it to lower the profile of a wide-V F1 engine, combining pushrod activated side-cams with standard OHCs (one of each per bank). This (and the custom Ilmor unit used by Mercedes at the Indy 500) show that their is no practical speed limitation to a pushrod design. For street applications however a multicam pushrod design becomes unnecessarily complicated. Although GM has toyed with it to reduce the packaging size of multivalve V8s, they have apparently decided to take a different route to reduce the size of future multi-cam 32V V8s.

As an aside. who would like to put money on a 6.2 L DOHC Cadillac V-series in the next-generation? And can we drop it in a B-series to thump the AMG C 63?

[dado]

As an aside. who would like to put money on a 6.2 L DOHC Cadillac V-series in the next-generation? And can we drop it in a B-series to thump the AMG C 63?

I think 6.0 l V8 DOHC with supercharger in next gen. V series and n.g LS engine in BLS-V

[ZL-1]

As an aside. who would like to put money on a 6.2 L DOHC Cadillac V-series in the next-generation? And can we drop it in a B-series to thump the AMG C 63?

I like the way you think, sir!

[smk4565]

I'll counter with...

A) Lexus engines aren't 'quiet, smooth' in a suave sense; they're hauntingly silent. I don't want a car whose powertrain I can't hear.

B) I'll put a Hydromatic 4-speed next to anything for smoothness and shift quality. I'm not saying I wouldn't mind an extra gear above 'four,' but in both the 4.0l Aurora and 3800 II s/c Bonnie, the transmission is beyond reproach, 120-130k miles notwithstanding. People look at 5 > 4 more than any real measure of transmission quality you'll have to endure for the life of a vehicle.

I have an Auora (2001), and I agree the transmission is smooth, but it could definitely use another gear or 2, the car would be so much more responsive. The 4-speed limits the engine. I am buying rear drive next time also, front drive limits a car a lot also.

Edited October 21, 2007 by smk4565

[91z4me]

Neither a lack of smoothness nor low-end power are inherent to the cam-in-block pushrod design. Both are down to the specifics of the actual application. GM has a tendency to favor low-end power (the atlas DOHC truck engines have even lower torque peaks than the pushrod engines). Pushrods are cheaper, and more compact, at least in V-engines. OHC engines however allow an easier implementation of multivalve intake and exhaust systems, which can improve performance at high rpms, and allow separate phasing of the intake and exhaust cams more simply than with a single-cam design (although Chrysler does use independent intake phasing in the pushrod Viper V10). Once you decide you need a multi-cam design there is really no great advantage to using a pushrods unless packaging is critical factor. Honda however has used it to lower the profile of a wide-V F1 engine, combining pushrod activated side-cams with standard OHCs (one of each per bank). This (and the custom Ilmor unit used by Mercedes at the Indy 500) show that their is no practical speed limitation to a pushrod design. For street applications however a multicam pushrod design becomes unnecessarily complicated. Although GM has toyed with it to reduce the packaging size of multivalve V8s, they have apparently decided to take a different route to reduce the size of future multi-cam 32V V8s.

As an aside. who would like to put money on a 6.2 L DOHC Cadillac V-series in the next-generation? And can we drop it in a B-series to thump the AMG C 63?

I gotta say I didn't read the whole thread but this thread is something other than what I would have expect from you griff. I kinda pictured you as a DOHC turbo 4 cylinder guy (likely due to your SAAB associated name/avatar). But still a pleasant surprise.

[Oracle of Delphi]

Lexus engines are wrapped in enough sound insulation to make the Pink Panther jealous. Throw in motor mounts made of marshmellows <or active motor mounts> and yea... it'll be smoother.

Guess what, the 3800 in the Lucerne is smooth and quiet to drive too and LeSabres and Bonnevilles were some of the first cars that came with an interlock so that you couldn't engage the starter while the engine was running because so many people couldn't tell when it was on.

The 3800 engine is one of my all time favorite engines.

[haypops]

The 3800 engine is one of my all time favorite engines.

Years ago, when the Northstar was still new and troublesome, I listened to an interview with the head engineer of the 3800 project. He was asked if he faced problems from having succeeded in developing a better engine than Cadillac. His answer was very political correct and therefore unremarkable. Execution of details is indeed important and GM is to commended for sticking with both engines.

[thegriffon]

Don't overestimate the time it will take to produce an 8-speed transmission if the program is approved. IIRC work on the 8-speed transmission predates the eCVT being produced now in Baltimore. The concept has already been fully worked out by GM transmission engineers and has not only been patented, but a trademark exists as well. While development work will need to be done to refine and calibrate the shift algorithms once that is done I believe any plant already retooled for the new 6-speeds could be producing an 8-speed version within months with little new tooling needed.

[plane]

Don't overestimate the time it will take to produce an 8-speed transmission if the program is approved. IIRC work on the 8-speed transmission predates the eCVT being produced now in Baltimore. The concept has already been fully worked out by GM transmission engineers and has not only been patented, but a trademark exists as well. While development work will need to be done to refine and calibrate the shift algorithms once that is done I believe any plant already retooled for the new 6-speeds could be producing an 8-speed version within months with little new tooling needed.

two thumbs up for that post.

:thumbsup:

What would be the difference between the 6 and 8 speed trannies, other than the obvious two gears?

Are the 8-speeds dsg-based?

Does the 8 speed require 25% more space?

Does it have completely different gear ratios?

Or the same gear ratios augmented at the top and/or bottom?

That is incredibly good news.

[91z4me]

Don't overestimate the time it will take to produce an 8-speed transmission if the program is approved. IIRC work on the 8-speed transmission predates the eCVT being produced now in Baltimore. The concept has already been fully worked out by GM transmission engineers and has not only been patented, but a trademark exists as well. While development work will need to be done to refine and calibrate the shift algorithms once that is done I believe any plant already retooled for the new 6-speeds could be producing an 8-speed version within months with little new tooling needed.

Alright guys lets pepper thegriffon w/ questions it appears as though someone found the combination to his information safe.

[Drew Dowdell]

thegriffon

you're only making this harder...

[thegriffon]

two thumbs up for that post.

:thumbsup:

What would be the difference between the 6 and 8 speed trannies, other than the obvious two gears? The way power is routed through the planetary gearsets in different "speeds". Although there are more ratios I don't believe there are any more physical gears (or at least any more planetary gear sets).

Are the 8-speeds dsg-based? No, although GM has already tested one of those as well.

Does the 8 speed require 25% more space? No

Does it have completely different gear ratios? Probably

Or the same gear ratios augmented at the top and/or bottom?

That is incredibly good news.

P.S. the German term "gang" typically used for the number of gear ratios is the same word as English gang (in chain-gang, work-gang, gang-plank etc.), in a different application. Both are ancient forms of the action-noun "going" and refer to a specific method, equipment, means, manner, route etc. used in going or proceeding.

Edited October 22, 2007 by thegriffon

[cletus8269]

P.S. the German term "gang" typically used for the number of gear ratios is the same word as English gang (in chain-gang, work-gang, gang-plank etc.), in a different application. Both are ancient forms of the action-noun "going" and refer to a specific method, equipment, means, manner, route etc. used in going or proceeding.

... And knowings half the battle...

Geee Iiiiiii Joooooooooooe!

[dwightlooi]

Three things:-

(1) Fuel Economy

The possible advantage of having MORE speeds is that you can achieve better fuel consumption numbers by having a very tall top gear without having a very tall first gear and/or big shift gaps between the gears. I say "possible" because having more gears does necessarily mean you can to the aforementioned. What's perhaps as important or MORE important is the Ratio Spread which is the maximum ratio difference between the tallest and shortest gearing a transmission can support. The 6-speed 6L80E/6L50E Hydramatics are 6.04:1 meaning the shortest gear is 6.04 times shorter than the tallest. The Mercedes 7-speed is "only" 6:1. The Lexus eight speed is 7.05:1. If you create an 8-speed transmission which has say a 6:1 ratio spread you are unlikely to see any economy gain.

(2) Performance

For a given 1st gear ratio and final drive (which you can easily configure) the shift gaps determine the drop in RPM for every shift. To understand why this is important, we need to talk briefly about what moves a car. In one word torque moves a car. The amount of push you get is the torque multiplied by the total effective gear ratio. For any given gear ratio, a car pulls the hardest at the engine's torque peak. Horsepower is merely a measure of torque x RPM. It is important because until the power peak torque is either increasing or decreasing at a rate slower than the increase in engine speed. In otherwords, as long as horsepower is increasing you are better off staying in the same gear even if the engine is past the point where it pulls the hardest in the gear you are in because for ANY % change to a taller gear ratio, you lose more torque multiplier than you lose torque as engine speed increases past the torque peak.

In otherwords, a general rule is that a transmission should shift at the power peak and end up in the next gear at or after the torque peak. Depending on the engine's peakiness, a 4-speed may or may not achieve this. A 5 speed almost always achieve this. A 6-speed simply gains you the very marginal advantage of keeping the revs after the shift closer to the power peak. However, it has been shown that the last point gets you very little in terms of performance -- many cars with the same power to weight ratios are no faster with a 6-speed vs a 5-speed.

(3) More gears can hurt.

More gears = more shifts from 1st to top gear. Shifts themselves ALWAYS hurt performance and economy. Why? Because during a shift, power transfer to the road is either interrupted or reduced (depending on transmission type). During a shift your are burning gas to make HEAT inside the transmission instead of pushing the car forward. Therefore, shifts themselves suck. The only reason you tolerate them is that the gains from having closer spaced ratios and a wider spread are larger than the losses to power interruptions during shifts. Unless this is true, having more speeds can actually hurt acceleration performance or economy or both.

[cmattson]

Forgive me if I'm wrong, but isn't the idea of an 8-speed that you don't sequentially progress through the entire gearset? I thought that your powertrain controller would intelligently decide which gear to give you next, to optimize your performance/gas mileage depending upon how you are driving the vehicle.. In example, I've just robbed the local bank and am trying to lose the local law enforcement. I'd get gears in the order of 1-2-4-6-7. When I'm doing a Sunday-afternoon-drive-and-stare-at-the-sun-while-going-10-under-the-speed-limit-in-the-fast-lane bit and I'd get gears 1-2-3-5-8. Is that correct?

[PurdueGuy]

Forgive me if I'm wrong, but isn't the idea of an 8-speed that you don't sequentially progress through the entire gearset? I thought that your powertrain controller would intelligently decide which gear to give you next, to optimize your performance/gas mileage depending upon how you are driving the vehicle.. In example, I've just robbed the local bank and am trying to lose the local law enforcement. I'd get gears in the order of 1-2-4-6-7. When I'm doing a Sunday-afternoon-drive-and-stare-at-the-sun-while-going-10-under-the-speed-limit-in-the-fast-lane bit and I'd get gears 1-2-3-5-8. Is that correct?

That was kind of the thought going through my mind - more gears doesn't equal more shifts if the transmission controls are intelligent enough. More gears would mean more options of ratios to shift to. At some point, though, the disadvantage of added weight and complexity (and possibly size, but it sounds like GM has that at a negligible point, at least with the 6-speeds) outweighs the advantage of more options. Of course, the added complexity is really only an issue if it adds to cost (purchase or repair cost) or reliability.

[thegriffon]

The great thing is that there is little or no added weight or complexity except in the programming. The new transmissions add ratios without adding gears by using a different strategy for routing power through the transmission (that's an oversimplification I know, but unless we have a planetary transmission engineer here it will have to do). Dwightlooi inadvertantly highlights why 6-speed automatics can achieve better fuel economy than a manual or CVT—unlike a normal manual transmission there is almost no interruption to the power transfer during a shift. The transmission can "preselect" a new ratio, and shift much faster than even the best human, so little power or fuel is wasted. As in the city stage of fuel economy tests where most shifting occurs, a 6-speed auto can often beat a manual, and come close enough in highway driving for an overall better performance (the precise ratios of each transmission are also a factor).

[dwightlooi]

The great thing is that there is little or no added weight or complexity except in the programming. The new transmissions add ratios without adding gears by using a different strategy for routing power through the transmission (that's an oversimplification I know, but unless we have a planetary transmission engineer here it will have to do). Dwightlooi inadvertantly highlights why 6-speed automatics can achieve better fuel economy than a manual or CVT—unlike a normal manual transmission there is almost no interruption to the power transfer during a shift. The transmission can "preselect" a new ratio, and shift much faster than even the best human, so little power or fuel is wasted. As in the city stage of fuel economy tests where most shifting occurs, a 6-speed auto can often beat a manual, and come close enough in highway driving for an overall better performance (the precise ratios of each transmission are also a factor).

An automatic transmission upshifts by having the the torque converter act as the "cushion" while one the gearbox slam shifts between two ratios through hydraulic actuation (electronically gated or otherwise). Basically, it'll be like shifting from one gear to another on a manual transmission very quickly WITHOUT taking power off the gas or using the clutch. In a manual, a very intrusive and potentially damaging shock will be experienced up the driveline from the wheels, through axles, through the differential, through the transmission, through the engine itself. However, the torque converter acts like a fluidly slipping clutch -- it is basically one propeller pushing fluid to turn a second propeller -- and permits a smooth transition. The problem of course is that a torque converter is like an always slipping clutch -- it robs power and immediate power conductance from the powertrain. This is why torque converters of today typically have a weak lockup clutch which engages the engine directly to the transmission input (neutralizing the torque converter) at low loads and when no shifting is occuring.

The main reason automatics traditionally are less desirable than manuals for enthusiastic driving (not to mention less efficient) is that there is this torque converter rubberband effect. Power application seems to lag by a few fractions of a second as the engine rpms can rise and fall while power to the wheels and change in speed plays catchup. The converter also takes part of the power produced by the engine and turns it into heat in the transmission fluid within the torque converter while performing the hydraulic coupling reducing efficiency. The lockup clutch mitigates this during cruising and that bought us a little efficiency gain. Recently there have been a few developments have cropped up such as clutch-to-clutch up shifting (which eliminates the freewheeling phase during a shift, unfortunately not for 1st-2nd shifts because the torque load is too high) and transmissions which are smart enough to blip the throttle during the freewheeling phase of a down shift. These gets you a more direct feeling and slightly better performing automatic.

An automatic meets or BEATS a CVT most of the time in efficiency because despite the latter's ability to maintain optimal gearing all the time, it suffers from one commonly overlooked flaw -- it needs to waste power ALL THE TIME driving a hydraulic pump to keep the two halfs of the CVT's pulleys pressed tighly against the steel belt! This happens even during gentle cruising at freeway speeds where an automatic basically locks up the torque converter. The CVT can't relax the pulleys at anytime or the belt will slip! The rise of the CVT, despite the advent of the tension belt (as opposed to compression Van Doorne type belts) CVTs capable of handling 200~250 lb-ft has been curtailed mainly because of this flaw in the entire concept which prevented the CVT from delivering better economy numbers than a 5A or 6A.

The challenge to the modern automatic will not come from CVTs it will come from the twin-clutch automated manuals (ala DSG). Here you basically have an electronically controlled manual using two clutches. one for odd gears and one for even gears. The clutch is slipped for parking lot crawling and basically the transmission shifts from one gear to another by slipping both clutches during the interim period while two gear sets are concurrently engaged. Borg Warner has shown that this can be done smoothly and with superior efficiency and performance compared to both manuals and automatics. With twin clutcch equipped cars on the street for 2~3 years now it has also been shown that these gear boxes aren't konking out en masse. The concern of course is that these transmissions are not serviceable at your local tranny shop and if they turn out to have a higher than normal failure rate at 10~15 years of age it will put a stigma on the car models that use them and their manufacturer. The longevity and reliability of an auto is a known quantity, that of the DSG is a maybe.

What disappoints me is that GM is not at least looking at the twin clutch actively at this time.