General Motors says it will offer an 8-speed transmission for the 2015 GMC Sierra Denali in the 6.2L EcoTec3 V8 engine configuration for Dubai and the rest of the Middle Eastern market. This setup gives the truck both improved fuel economy and higher first gears for towing.
For truck owners, the new GM 8L90 transmission will offer the 2 extra gears in a 7.0 overall gear ratio. This ratio is wider than the current 6L80 six-speed setup. This means it will likely have a higher first gear to help get the load rolling. This is important since getting the load rolling is a critical part of towing operation.
On the high-end gears like six, seven or eight, these gears will likely be setup to maximize fuel economy at higher speeds. These gears are aimed at allowing the engine to produce a minimal amount of power to maintain these higher speeds. For example, where a six-speed may have maintained high speeds at 2,500 RPMs, the new 8-speed will do the same at 1,500 RPMs. This results in better fuel economy at those speeds.
GM already announced the U.S. market will get the 8-speed transmission as well.