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GM Pushing Hard on Six-Speed Automatics; Introduces Three More

The 6L80 RWD six-speed automatic.

GM is making a big push with its six-speed automatic transmissions. The company plans to offer one million vehicles annually with six-speed automatic transmissions by 2008, and three million by 2010. For model years 2006 and 2007, six-speeds will appear in nearly 40 global vehicles.

Advantages of a six-speed automatic include fuel economy improvement of up to 4% and power improvement of up to 7% compared to a four-speed automatic, and delivering a shift feel that is seamless to the customer. The six-speed automatic enables a reduced engine rpm at highway cruising speeds, thereby reducing engine wear and noise, and also helping fuel economy.

With a six-speed, smaller steps are used between gears compared to a conventional four-speed automatic. This allows the transmission to quickly find the best gear for the vehicle speed and road conditions.

The company recently introduced three new members of the six-speed family. Most of GM’s six-speeds feature a wide, 6.04:1 overall ratio compared to 4.0 of typical four-speed automatics.

New 2007 model year six-speed automatic transmission variants include the Hydra-Matic 6T70 and 6T75 for front and all-wheel drive vehicles, as well as the Hydra-Matic 6L50 for rear and all-wheel drive vehicles.

The new 6T70 and 6T75 six-speed automatics are designed for front- and all-wheel drive vehicles. The transmissions are based on a common design, with the 6T75 rated for higher torque capacity. The 6T70 debuts on the Saturn Aura and on a Pontiac G6 model; the 6T75 will be offered on the Saturn Outlook.

The 6T70/75’s clutch-to-clutch operation and 6.04:1 overall ratio help the transmission deliver up to 7% improved performance and up to 4% improved fuel economy when compared with current front-wheel drive four-speed automatics.

Both transmissions use a very high numerical 4.48:1 first gear, which helps deliver exceptional launch feel, and a 0.74:1 overdrive sixth gear, which reduces engine rpms at high speeds, thereby reducing engine noise and vibrations. Fifth gear is 1:1 direct drive.

GM co-developed the 6T70/75 with Ford Motor to reach production in less time and to reduce development costs for each company by as much as 50%. A common on-axis design and many common components are shared between GM and Ford Motor Co. The controls, calibrations and operation of the transmissions are unique to each company.

GM also announced an additional $332 million investment in the Warren Transmission Plant to support production of the new six-speeds.

The new 6L50 six-speed transmission debuts in certain 2007 Cadillac STS rear- and all-wheel drive performance sedans and the V-8-powered SRX crossover SUV. The 6L50 is the second model of four new variants in the RWD six-speed transmission family. The 6L50 is designed with the same modular flexibility as the larger 6L80 and is fully compatible by using the same advanced electronic controls. As with the 6L80, the 6L50’s gearset configuration enables the same 6.04 wide overall ratio.

The 6L80 six-speed automatic transmission was the first of four variants in the rear-wheel drive transmission family designed with modular flexibility and compatibility with advanced electronic controls.

It also features clutch-to-clutch operation, manual range selection and an integrated 32-bit electro-hydraulic controller. It debuted in 2006 on the Cadillac XLR-V, STS-V and Chevrolet Corvette, where it is offered with paddle-shift control.

The 6L80 also is tailored for the heavy-duty requirements of SUVs and trucks, and is offered on GM’s 2007 full-size SUVs equipped with the Vortec 6.2L V-8, such as the GMC Yukon Denali and Cadillac Escalade.

With two overdrive gears, engine rpm is reduced by approximately 9% at 60 mph—a reduction of about 1,350 rpm.



Wow! What a huge step forward towards oil independency.

In Europe, most of the cars have manual transmission and those available with automatic have 6 speeds. Just look at Volkswagen: Already in 2004, the automatic option for a VW Golf was six speed and the same for 80% of all other models.

The USA was once world technology leader. Where are they today. Shame.


actually late compared to german brands but hopefully not too late, this may be the beginning of an change in american cars enegeneering


How would this better than CVT?

Rafael Seidl

Don't forget that the initial purchase price on a car is higher in Europe than in the US, and that consumers tend to hang on to them longer.

Btw, Mercedes has a 7-speed AT. Unfortunately, the higher gears are usually added to support greater top speed and comfort. Their potential for improving fuel economy is only gingerly exploited, because carmakers want to limit kickdown events in premium models.

And yes, the US could cut its fuel consumption by 8-10% in the coming decade if it required its student drivers to take their test in a car with a manual transmission. The oil & gas lobby would surely oppose such a proposal, though. Perhaps dual clutch transmissions will bridge the gap when they make it into US cars.

Sid Hoffman

CVT's have higher mechanical loss and are less reliable than a conventional AT with lockup torque converter. GM's huge, 300+ horsepower Tahoe gets the same fuel economy as Honda's smaller, lighter, 200-something horsepower Ridgeline. GM gets no respect for their prowess, but if anything, that will only make them that much more powerful when they retake their crown as the technological leader of the world.

Lou Grinzo

"GM gets no respect for their prowess, but if anything, that will only make them that much more powerful when they retake their crown as the technological leader of the world."

I sincerely hope this happens, as I think it would be a very positive turn of events for GM to be leading the pack in technology (and presumably fuel efficiency, reliability, etc.). That would give Honda, Toyota, et al. some serious competition, and result in better availability of more efficient cars on the US market.

But I wouldn't bet my lunch money, let alone something far more valuable (like the price of a new vehicle), on that coming to pass. Until GM wakes up and stops trying to save themselves in the US market via selling trucks, and starts seriously competing with the Fit, Civic, Yaris, Corolla, etc., they're on a slow slide to niche status.


"GM's huge, 300+ horsepower Tahoe gets the same fuel economy as Honda's smaller, lighter, 200-something horsepower Ridgeline."
First of all it is not fair comparison. One is a pickup another is SUV. If anything Tahoe should be compared to Pilot. Both more or less same size SUV.
Even if you compare those two you need to assume that:
both of them will drive at 55 mph with very light foot. I bet that Ridgeline is going to be a lot more efficient at 80 mph then Tahoe. Just because GM engineers are good at setting a car for EPA test doesn't mean that you will see it in real life. That why they don't get any respect.
We'll see how Tahoe do with 6 speed transmission when it is compared to Riceburners, for know no praise for GM.

j padula

I think this is the same transmission that was developed in a joint venture with Ford. They spent 750 million dollars together to make it. One transmission.
They spent between 500 million to a billion on the EV1 electric car program and have still not stopped moaning about it.
Gm's Lutz was recently asked by Motortrend what his biggest mistake was. Killing the EV1 he answered.
He claimed it did not cause any loss of money to the company, but was bad PR.
If he wants to see bad PR just wait till "Who killed the electric car come out" later this month...


A small improvement is better than no improvement at all.

I would like to see what the development & production cost difference is between this 6 speed AT and a dual clutch "SMG" type gear box.

A CVT built to develop a high enough starting gear ratio could completely remove the need for a torque convertor making it more efficient than an automatic or manual but many people are *unsettled* by the manner in which a CVT equipped car behaves (staying at peak torque or efficiency rpm constantly while the speed increases).


From fueleconomy.gov

Tahoe 4wd 14/18

Ridgeline 16/21


Also: Tahoe 4wd is 295 hp vs 247 hp for Honda Ridgeline. I think that puts it in better perspective than calling the Tahoe a 300 and the Ridgeline 200 something.


The Ridgeline doesn't use a CVT so I don't know what the point of the comparison to the Tahoe was anyway.

Sid Hoffman

Good job on quoting the OLD Tahoe. The 2007 (which is what all Tahoes on dealership lots for the last 3 months are) is rated at 16/22 in 2WD and 16/21 in 4WD. The 2007 Tahoe is 320 horsepower. It achieves those figures with the old 4-speed, so yes, it will be even better when they give it the new 6-speed like the Corvette (almost the same engine) has.


What is the towing / load capacity of the ridgeline?
Does it have a low range on the 4wd system?


Sorry, but I did not realize you were talking about 2007 and did not realize data was available for the 2007. However, I still don't see the relevance of the comparison in the context of the CVT transmission.


The Tahoe/Ridgeline is not a great comparison, SUV/pickup and large/midsized. But if you must...

The NEW Tahoe is several generations old platform, now somewhat optimized for fuel economy. It does well for a large truck. But the Ridgeline is a "first try" pick-up for Honda, admitingly with some upgraded Pilot/Odessy parts, so the next generation should do better now that economy is so important for truck buyers. Also, the Tahoe does have an aerodynamic advantage of a closed aft end.

Sid Hoffman

No, the new Tahoe is based on the GMT900 platform which is BRAND NEW, not "several generations old." Are you all on the Honda/Toyota payroll or something? No one in the universe makes a real truck or SUV with a CVT transmission because they are weak and crappy. Nissan offers a CVT with their minivan, I mean wannabe SUV, the Moron-oh, which isn't a fair comparison since it's just a jacked up Nissan Maxima station wagon in reality.

I don't understand why any of you are hung up on this "GM sucks because they only have a 6-speed and not a CVT" when there's almost no CVT's on the market except for hype-rids, which only get 26-32mpg according to Consumer Reports anyway. The Civic's CVT only lasts about 60-100k miles anyway, and that's with it only having 100 ft-lbs of torque in the first place. They've had reliability problems with their CVT's ever since the 1996 Civic HX and still can't make them as reliable as a conventional automatic. Weak!


My comments had nothing to do with being hung up on anything,much less whether or not GM is better or worse than Honda. It was just a question asking what, if anything, is wrong with a CVT.

As far as your reference to CR, that is complete crap from my experience. My Prius averages over 50 mpg on mountain roads and the CR report is totally inconsistent with the extensive databases on various sites that show the averages of dozens of Priuses.

The reason I asked about the CVT is that I found it to be a wonderful transmission when I had my Civic hybrid . I found it wonderfully smooth and beneficial on mountain roads as the gearing always seemsed to be optimized. As for reliability, I am not aware of any data on the civic hybrid, transmission in this area.

I am not suggesting the cvt should be used in monster trucks or suvs; I am just asking out of curiosity because of my own personal experience, which has been positive.


I don't think the current CVT designs would be well suited to towing heavy loads without massive R&D on materials and design, probably a much more expensive route to take, but they are essentially taking it with the hybrid transmission being partly eCVT and partly conventional, but I don't expect it to be cheap.

hampden wireless

Actually I feel a Ridgeline vs Tahoe comparison is quite fair. It shows the results of GM's push for more efficient large vehicles is working. The Tahoe is much larger yet achives greater mpg then the v6 Ridgeline.

GM achives this because of large improvments to the engine and the lower drag of the new body. When you add in these new transmissions you get another mpg or so.

I don't want to own a vehicle as big as the Tahoe or Ridgeline but I am GLAD GM is making improvements.

On other messages when talking about GM's flex fuel vehicles GM gets bashed quite bad, yet here today VW is getting praise for doing almost the same thing. Seem fair?


The Pilot gets better gas mileage...albeit with a less powerful V-6 but the vehicle "size" (interior space) is rated the same as the Tahoe.

Up until the mid 90s CVTs were used on little 3 cylinder 60hp motors. They have made vast improvements but they are not going to be capable of handling the torque and loads from a large vehicle.

I want to know if there was really that much greater cost do develop a tranny similar to what VW/Audi use (their dual clutch). It would have been more efficient...not sure if the average american would have embraced it in mass production or if they have ever put one of those in a heavy chassis designed for towing with a motor that puts out alot of torque.

Robert Schwartz

This would be interesting if there were any chance that GM would be in business in two or three years.


I will never buy a GM product. Not after this:



I'd rather see a 7spd manual :) ... for that matter I'd even like to see more 6spd manuals, most manuals in the US except for sports cars/sport package cas are still 5spds.

GM Will still be in business in 2 or 3 years, don't be silly, GM has enough capital to operate at a loss for some ~10 years. AND they can still declare bankrupcy and be in business for longer.
GM is still the world's largest auto-maker, they aren't going to go out of business in a mere 3 years.


What VW is doing in Brazil is not comparable to what GM is doing in the United States. GM, in the U.S. is primarily taking advangage of a loophole which permits them to meet CAFE standards by just considering the gasoline used with E85. This is especially absurd when one considers that the vast majority of drivers will be using gasoline, not E85, when driving their vehicles. It also pretends that their in no oil or fossil fuel use in the manufacture of ethanol.

Having said that, I don't think VW deserves praise or admonition for their actions in Brazil. They were just making a production decision which just makes senses given the pervasiveness of ethanol in that market.

The fact that GM has improved the efficiency of the Tahoe is a good thing. However, I would hope that the only people driving these large vehicles are those who truly need it for whatever particular occupation they are in that really needs this kind of power. When I see single occupants driving their 330 hp Tahoes to their office jobs, I have little sympathy for their alleged needs for that kind of vehicle.

I must admit that GM's "go yellow" campaign leaves a bad taste in my mouth
as it will do very little for the environment and is just a b.s. marketing campaign.

GM isn't simply taking advantage of the regulatory and politicial environment. They help shape that environment throught their lobbying and campaign contributions.

I might add that I am not leaving Toyota off the hook on this subject as they are in bed with GM in opposing California's attempt to cut greenhouse emissions from autos. However, correct me if I am wrong, but last I checked Honda is not part of that particular coalition.

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