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dwightlooi

Which Transmission will you like best?

  

17 members have voted

  1. 1. Which Transmission will you like to see as standard on GM vehicles?

    • eAssist - 6-speed Automatic + 15hp Electric + 0.5kWh Battery
      8
    • [img]http://img809.imageshack.us/img809/1117/gm8speedlogo.jpg[/img] - Conventional 8-Speed Automatic
      4
    • DCT - 6-speed Dual Clutch Automated Manual
      5


45 posts in this topic

Of the various (relatively affordable) transmissions and drive technologies being developed, or can be developed, what will you see most as a standard feature on GM vehicles? The keyword here being "most", hence you may only choose one.

Edited by dwightlooi

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the eAssist if its not riddled with reliability issues. the malibu/aura hybrids were lemons, and i really think the whole stop start thing needs to be proven to work over time and in all sorts of weather. likewise with anything involving belts and generators etc.

the 8 speed automatic is inevitable anyways, if other mfrs do it then GM will be forced to do it.

dual clutch may prove a role in some smaller vehicles but I think CVT is probably a better idea for economy-mid level cars.

true manuals are probably headed for the grave. I like sticks myself, but i think dual clutch has the best chance of usurping the real manuals.

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BMW has been offering stop start in the EU for a couple years at least.

The only lemon thing about the Malibu Hybrid was the batteries. The eAssist uses a completely different design and battery chemistry. Any other gripes have to do with the specs, but that doesn't mean it was unreliable.

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i'd like to see a manual override on the stop start. for example in winter its much better to leave your car running especially in extreme cold. the user should have the ability to be able to decide whether they want it on or off.

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I forgot GM registered that 8peed logo, like 2 years ago, whatever happened to that?

2007. I think bankruptcy plans killed its introduction by this year. I have to go back and see when was the exact time.

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the eAssist if its not riddled with reliability issues. the malibu/aura hybrids were lemons, and i really think the whole stop start thing needs to be proven to work over time and in all sorts of weather. likewise with anything involving belts and generators etc.

the 8 speed automatic is inevitable anyways, if other mfrs do it then GM will be forced to do it.

dual clutch may prove a role in some smaller vehicles but I think CVT is probably a better idea for economy-mid level cars.

true manuals are probably headed for the grave. I like sticks myself, but i think dual clutch has the best chance of usurping the real manuals.

There are reasons why most adopters back outed of CVTs -- Audi, Ford, Nissan, you name it.

They... well... uh.. sucked!

Primarily the problems were three fold:-

(1) CVTs have limited torque ratings -- about 100~120 lb-ft on compression (Van Doorne) chain designs abour 200~240 on tension chain ones.

(2) CVTs reduce refinement -- by causing the engine to drone at one RPM. Some designs simulate discrete ratios, but doing so reduces the efficiency.

(3) CVTs are NOT more efficient in service than contemporary automatics -- infinite ratios are nice, but both chain and toroid designs have narrower ratio spreads than leading automatics. This leads to higher freeway cruising rpms or inferior off the line acceleration or some combination of both. On top of that, because CVTs sandwich the variator chain with pulleys at high compression forces, it requires a constant supply of high hydraulic pressures. This in turn require the constant operation of a powerful hydraulic pump. Think 2~3 A/C compressors worth or parasitic drag. These practically eliminates any efficiency gains from the CVTs and frequently actually made mileage worse.

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Why has Nissan spread CVT's across nearly its whole Nissan brand lineup then?

Subaru, Mits, Lexus, hybrids, all using CVT's.

Ford stopped because they did an ASS job on it. Just like GM..

When you look at all the R&D time and money spent on traditional automatics and compare that CVT's have maybe seen 1% of that investment historically it suggests the engineers are finally doing a good basic job and now things can only improve tremedously. Traditional automatics are pretty tapped out in terms of what else they can do with them. If CVT's had the same amount of R&D behind them they would leave traditional autos in the dust.

Every CVT I have driven lately has been quite good. The engine drone you suggest is constantly being improved as the logic behind the CVT behavior improves. Drivers also adjust their throttle style to take advantage of the right ratio for each situation. The CVT's are great, especially when they drop down to super low rpm's on the freeway. Not sure how something like a new Subaru outback can turn high 30's mpg on real world mpg numbers with an AWD vehicle and a normal stepped tranny. the CVT in those run 500-1000 rpm lower in top gear than the manual trans do, and respond faster to boot.

The breed is improving, you may need to go out with an open mind and sample some. The latest Nissan v6 CVT's even get praise. You are basing your 'facts' on old information and to be honest piss poor engineering from those companies on older models. If CVT's have torque limits why does the Lexus hybrid sedan with all that power use a CVT?

I think CVT's have great use in small to mid size cars. I do think stepped trannies probably will still be more prevalent in larger vehicles.

Edited by regfootball

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Why has Nissan spread CVT's across nearly its whole Nissan brand lineup then?

Subaru, Mits, Lexus, hybrids, all using CVT's.

Ford stopped because they did an ASS job on it. Just like GM..

When you look at all the R&D time and money spent on traditional automatics and compare that CVT's have maybe seen 1% of that investment historically it suggests the engineers are finally doing a good basic job and now things can only improve tremedously. Traditional automatics are pretty tapped out in terms of what else they can do with them. If CVT's had the same amount of R&D behind them they would leave traditional autos in the dust.

Every CVT I have driven lately has been quite good. The engine drone you suggest is constantly being improved as the logic behind the CVT behavior improves. Drivers also adjust their throttle style to take advantage of the right ratio for each situation. The CVT's are great, especially when they drop down to super low rpm's on the freeway. Not sure how something like a new Subaru outback can turn high 30's mpg on real world mpg numbers with an AWD vehicle and a normal stepped tranny. the CVT in those run 500-1000 rpm lower in top gear than the manual trans do, and respond faster to boot.

The breed is improving, you may need to go out with an open mind and sample some. The latest Nissan v6 CVT's even get praise. You are basing your 'facts' on old information and to be honest piss poor engineering from those companies on older models. If CVT's have torque limits why does the Lexus hybrid sedan with all that power use a CVT?

I think CVT's have great use in small to mid size cars. I do think stepped trannies probably will still be more prevalent in larger vehicles.

(1) The last CVT I sampled was in an Altima Hybrid. I wasn't impressed. The same 2.5 liter QR25DE engine was less obstrusive and has better perceived refinement when paired with the previous generation's 4-speed Automatic.

(2) I have also driven the Audi A4 3.0 Multitronic, the Ford 500 CVT and the Nissan Murano CVT. None were as good as the newest 6-speed, 7-speed and 8-speed autos.

(3) Planetary CVTs in Hybrids like those in the Prius, HS250, Fusion Hybrid, Volt, etc. aren't CVTs at all. In fact, they are not really transmissions at all. What they are is a work splitting device; more like a differential. Imagine a reverse differential, where you connect each wheel to a separate engine, the drive shaft then becomes the output. The engine and the motor drive the sun and ring gears. The planet carrrier drive the wheels. The more torque either one puts in the faster that device spins an the lower its gear ratio, conversely the ratio on the other becomes higher and its rpm becomes lower. The ratio is directly proportional to the input torque from each. To reduce the increase for one, the other must do more work. This allows driving force to be split between to independent propulsion sources. It only works when you have two motors. It only works well when the two are similarly powerful but at optimized for different rpms.

(4) EPA highway economy really has nothing to do with CVTs or automatics or even the ratio spread. The test is done at highway speeds with practically no shifting and very little change in speed. Essentially only the top gear ratio matters. You can have minimal ratio spread and still have a tall cruising ratio hwoever you'll sacrifice off tthe line acceleration. With a wide ratio spread you can have both. Right now the ratio spread for CVTs are between about 4.2 to 6. The ratio spread for conventional autos are between 5.4 and 7.5. The advantage goes to automatics. The reason for the difference lies in the fact that autos can have 2 or 3 planetary sets in sequence. CVTs typically only have one variator. Even though the effective ratio it can achieve with one is wider than that which is achievable with one planetary gearset, it is narrower than can be hit with 2 or 3 of them. What's important here is that lets say both the CVT and the automatic has the same top gear ratio, the automatic is more efficient in cruise because it does not have to waste power driving the hydraulic pump to keep the variable pulleys functioning.

Edited by dwightlooi
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Which Murano did you sample....the first ones or the newest ones? The standard Altima's CVT is quite good. the 2.5 altima with CVT i spent 1000 miles in is faster and far more responsive then my father in laws grand prix with 3800 v6 and auto and its right up there with any excellent performing powertrain today. All the CVT's I have driven lately are quite good. You did not demonstrate that any of the CVT's you drove were recent.

The Ford's was the worst of the bunch BUT THATS ALREADY 5-7 years PAST. Get in today. Just because the loser engineers at GM or Ford in the past couldn't design and build a decent one does not mean that the rest of autodom hasn't improved the breed tremendously.

EPA economy and more importantly REAL WORLD economy does in deed depend on the tranny. The CVT's drop the engine rpms a lot lower in comparison to conventional autos and even manual gearboxes. The infinite adjustability, quick response is why they can do that. A Mazda6 manual turns 3k rpm at 70mph but a Subaru Legacy runs almost 1000 rpm less at same speed with its CVT. Most 4 bangers with even 6 speed autos are still turning close to 3k rpm at 70+. The response capability and wider spread of the CVT allows them to get the gearing to drop down at higher speeds and better FE. If they could do this with conventional autos and sticks, why aren't they?

You keep talking in engineering speak, but you haven't addressed the basic question. Why do the CVT's run lower rpm on the highway, why are so many manuf's putting CVT's in their smaller cars to get better FE? Even GM just said recently they will be going back to CVT's. Apparently that is in direct conflict with what you just tried to lobby against.

Edited by regfootball

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How about all of the above? :lol: The Passat BlueMotion has a seven-speed dual-clutch automated manual with stop-start. An eight-speed dual-clutch automated manual with eAssist would one-up it.

(1) The last CVT I sampled was in an Altima Hybrid. I wasn't impressed. The same 2.5 liter QR25DE engine was less obstrusive and has better perceived refinement when paired with the previous generation's 4-speed Automatic.

Altima Hybrid doesn't have a real CVT but a planetary device instead.

I'd prefer a planetary setup, by the way. They're more reliable than a chain-driven CVT, and they're inexpensive and simple. No clutches, nothing to go wrong.

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i haven't driven the dual clutch on any of the gas turbo VW's (GTI etc.) but the dual clutch on the TDI was junk IMO.

Apparently there is a reason the Passat etc. still has a steptronic instead of a dual clutch.

Dual clutch is just like CVT in the respect that it has had about 1% total of the investment into the product that traditional slushboxes have had. Just like CVT if dual clutch had all the resources that slushoxes have had, they probably would be sublime and polished too.

I think dual clutch holds promise as the automatic that has the chance to satisfy the shift it yourself bunch out there.

Edited by regfootball

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Which Murano did you sample....the first ones or the newest ones? The standard Altima's CVT is quite good. the 2.5 altima with CVT i spent 1000 miles in is faster and far more responsive then my father in laws grand prix with 3800 v6 and auto and its right up there with any excellent performing powertrain today. All the CVT's I have driven lately are quite good. You did not demonstrate that any of the CVT's you drove were recent.

The Ford's was the worst of the bunch BUT THATS ALREADY 5-7 years PAST. Get in today. Just because the loser engineers at GM or Ford in the past couldn't design and build a decent one does not mean that the rest of autodom hasn't improved the breed tremendously.

EPA economy and more importantly REAL WORLD economy does in deed depend on the tranny. The CVT's drop the engine rpms a lot lower in comparison to conventional autos and even manual gearboxes. The infinite adjustability, quick response is why they can do that. A Mazda6 manual turns 3k rpm at 70mph but a Subaru Legacy runs almost 1000 rpm less at same speed with its CVT. Most 4 bangers with even 6 speed autos are still turning close to 3k rpm at 70+. The response capability and wider spread of the CVT allows them to get the gearing to drop down at higher speeds and better FE. If they could do this with conventional autos and sticks, why aren't they?

You keep talking in engineering speak, but you haven't addressed the basic question. Why do the CVT's run lower rpm on the highway, why are so many manuf's putting CVT's in their smaller cars to get better FE? Even GM just said recently they will be going back to CVT's. Apparently that is in direct conflict with what you just tried to lobby against.

Well, let me re-state this again...

The CVT does not, in any way, make possible a lower cruisin RPM than an automatic or manual transmission. That has nothing to do with the CVT or its infinite ratios. It has to do with the the final drive gear. Period.

For example, you can be at 1000 rpm at 60mph with ANY transmission. I mean ANY manual, automatic or CVT transmission. All you have to do is to select a final drive to match the tallest ratio of that transmission that will make the engine turn at 1000 rpm when the wheels are covering 60 mph.

The only question what ratio your 1st or lowest gear will be when you do that. If it is very tall then the car will be really sluggish off the line from a stand still. The ONLY thing that affects your 1st or lowest ratio when your tallest makes 1000 rpm at 60mph is the ratio spread of the transmission. Ratio Spread = lowest ratio / tallest ratio. A transmission with a ratio spread of 7:1 will have a 1st gear that turns the engine 7 times faster at any given speed than its tallest gear.

The CVT, currently does not have the widest ratio spread. The traditional automatic does. Aisin hit 7.5:1, ZF hit 7.01:1. The Nissan's CVT is 5.4:1 and Audi's is 6.0:1. GM's 6-speed 6L45 and 6L50 Autos are 6.06:1

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Before you two come to blows over this: Reg, just because the Subaru Legacy CVT runs at a lower RPM than a Subaru Legacy Automatic doesn't mean that an automatic can't run that at that RPM. It just means that Subaru, for whatever reason, choose a different top end ratio for the automatic. I don't remember exactly the RPM the 4-Cylinder Terrain ran at during a 70mph cruise, but it wasn't much over 2,000 rpm.

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ok, just to clarify, there is no animosity here.

but i don't think the latest and greatest gen of CVT's is being given a fair shake here by Dwight.

and, the recognition that in models that FE is a target, you are seeing a movement to CVT's, the Cruze is even being targeted for CVT to improve the FE.

It's not fair to judge CVT's on the crappy work that GM and Ford did with them over half a decade ago. Clearly the engineers failed at economy, performance, and reliability with it. They basically didn't do what they get paid to do. Look at what is being put out now. Put in the effort and resources, and you are where they are getting with them now. CVT and dual clutch again have had 1% the investment that slushboxes have had, there is nothing but improvement to be had.

Go on the edmunds and such where actual owners have purchased a car with CVT and more than not say they like the stepless tranny once they adjust and get used to it. Over time as they tune the actions of it, things like the drone are minimized or gone, and adjusting to throttle and such you begin to appreciate the lack of steps. Just a fluid transition. Over time they will program the rubber bandiness out of it.

CVT in no way is the only way to go, but it has a place, and GM Ford etc. can't afford to not have their entries with it. Where CVT's do well is moving the rpm to the torque band quickly and then getting off them even more quickly and settling into a non gas using range quicker than the stepped trans.

The 'ratio spread' is somewhat insignificant. The response of the CVT if its quicker than a stepped tranny gets and keeps you in the powerband quicker and only as long as you need, assuming the driver is manning the throttle correctly.

Edited by regfootball

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Well, let me re-state this again...

The CVT does not, in any way, make possible a lower cruisin RPM than an automatic or manual transmission. That has nothing to do with the CVT or its infinite ratios. It has to do with the the final drive gear. Period.

For example, you can be at 1000 rpm at 60mph with ANY transmission. I mean ANY manual, automatic or CVT transmission. All you have to do is to select a final drive to match the tallest ratio of that transmission that will make the engine turn at 1000 rpm when the wheels are covering 60 mph.

The only question what ratio your 1st or lowest gear will be when you do that. If it is very tall then the car will be really sluggish off the line from a stand still. The ONLY thing that affects your 1st or lowest ratio when your tallest makes 1000 rpm at 60mph is the ratio spread of the transmission. Ratio Spread = lowest ratio / tallest ratio. A transmission with a ratio spread of 7:1 will have a 1st gear that turns the engine 7 times faster at any given speed than its tallest gear.

The CVT, currently does not have the widest ratio spread. The traditional automatic does. Aisin hit 7.5:1, ZF hit 7.01:1. The Nissan's CVT is 5.4:1 and Audi's is 6.0:1. GM's 6-speed 6L45 and 6L50 Autos are 6.06:1

yeah its dandy that its got a wider spread but if its cannot change those ratios as quickly then its not an asset.

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yeah its dandy that its got a wider spread but if its cannot change those ratios as quickly then its not an asset.

A wider spread is an asset for either launch speed, cruising MPG, or a little of both. What Dwight is saying it that if a CVT's final drive matches a 6-speed's final drive, the 6-speed will have a better launch because the first and second gears are lower than what the CVT can manage. If the CVT's lowest ratio matches the lowest ratio on a 6-speed, the 6-speed will have better cruising mpg because the final drive ratio will be lower.

And Reg, I find a fault with your assertion that a conventional automatic can't change the ratios as quickly. In some situations it would actually be quicker. The GM 6-speeds (and Toyota 6-speeds if I recall) can jump down two gears when needed, so you'll get a 6->4 shift or a 5->3 shift if you really mash the gas. A CVT has to sliiiiiiide down.

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yeah i can't say i am familiar with those.

as far as Audi's go the DSG is probably better, etc.

I just think the last 2 years or so the CVT's have improved a lot. It takes getting used to, sure.

I think stepped slushboxes are fine too, but so many of them get knocked for lazy shifting. Like the Cruze, I know I thought the Malibu 6 speed was lazy. I like the idea of the eAssist with 6 speed but i really wish they would get rid of the lazy behavior.

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That's from two factors, first, they are reluctant to kick down for fuel economy reasons, second they are "soft" in their kick down for comfort reasons.

I know it's not a passenger car, but that F-350 really smacked through the gears. If you put it in Tow/Haul mode it seemed even worse. The GMC was super super smooth and probably what you'd call "lazy" but when you wanted the speed, it would drop two gears for you and charge forward like a freaking locomotive.

It really just has to do with the tuning of the transmission.

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