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Autoline Daily reported today that "NEW 8-SPEED DOESN’T BOOST MPGs
Automakers have been adding transmissions with more and more gears to help improve fuel economy, but with Cadillac’s recent announcement that it’s switching from a 6-speed to a 8-speed unit in the 2015 CTS and Escalade there was no mention of any MPG improvements. So, we contacted Cadillac to find out what’s up. According to the company there will only be a small improvement with the Escalade and it’s not known if it will be reflected in the EPA rating, which in turn may not lead to a re-statement of fuel economy on the label." It may be a reasonable inference to think the same will be true for the Stingray's move from the 6 speed to the 8 speed.
 

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Maybe it's all about the truck division, they are pairing the new 8 spd with that version of the 6.2 L V8. Boosting the trucks fuel economy could be important to GM's fleet numbers. Having the same tranny and similar 6.2L engine across the various segments can reduce costs as well, perhaps with less impact on smaller, lighter cars.

All Chevrolet and GMC trucks with 6.2 EcoTec3 V8 engines will come standard with an 8-speed Hydra-Matic automatic transmission to replace the current 6-speed for 2015

8-Speed Transmission Now Standard On 6.2 V8 Chevy & GMC Pickups, SUVs
 

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I suspect the Silverado guys are over on their forum bragging they will be able to tow more with their new 8 spds :rolleyes:

After much speculation, GM confirmed it will be using a brand-new eight-speed transmission for the 2015 Chevrolet Silverado 1500 and GMC Sierra 1500 pickup trucks equipped with the 6.2-liter EcoTec3 V-8 engine (several full-size SUVs also will get the eight-speed).

The new electronic transmission, called the 8L90, will replace the previous 6L80 on select models, but it is likely to make its way (after some slight modifications) into the smaller 5.3-liter EcoTec3 V-8 as well. The only other pickup with an eight-speed transmission is the Ram 1500 that uses two different versions (the ZF 8HP45 and 8HP70, with a gear spread from 4.71:1 to 0.67:1) to accommodate Ram's three-engine lineup. There is no word about whether GM will offer a smaller, lighter-duty eight-speed to accommodate the smaller EcoTec3 V-8 and standard V-8.

GM notes that the new eight-speed will have an overall gear ratio spread of 7.0. This is likely to mean a much deeper first gear (possibly around 4.65:1) and implies that GM might be able to offer new gear sets to provide much better fuel economy while still offering strong towing numbers.

In a brief press release, GM said that the new transmission will still allow these new powertrains to adhere to Society of Automotive Engineers' J2807 towing standards, providing a segment-leading towing capacity of 12,000 pounds.
 

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Not too sure MPG's factor into my purchase thinking @ current gas prices, but if they ever go to $5. per gallon or above that might be enough for me to have second thoughts.
 
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