GM Confirms Eight-Speed Transmission for Half-Ton Pickups

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. GM's Toledo, Ohio, transmission plant will begin production of the new eight-speed in the fourth quarter this year and be available for 2015 models. Fuel economy estimates for the new powertrain will be released closer to the production date.

Late last year Ford and GM announced that they were working together on nine- and 10-speed transmissions (presumably for cars). At that time we caught a heavily camouflaged Ford F-150 heading out of GM's Milford Proving Grounds facility. Of course, it's possible the new F-150 could be doing something unique as well. No word whether GM or Ford will use something similar to Ram's rotary dial.

The available gear ratios for both 2014 Ram 1500 eight-speed transmissions are: 1st (4.71:1), 2nd (3.14:1), 3rd (2.10:1), 4th (1.67:1), 5th (1.29:1), 6th (1.00:1), 7th (0.84:1), 8th (0.67:1) and Reverse (3.30:1).

Available axle ratios for the 8HP45 (Pentastar 3.6-liter V-6): 3.21:1 and 3.55:1.

Available axle ratios for the 8HP70 (EcoDiesel 3.0-liter V-6 and 5.7-liter V-8 Hemi): 3.21:1, 3.55:1 and 3.92:1

From www.pickuptrucks.com by Mark Williams |