The reason: the new 2015 Ford F-150.
You could say that General Motors was blindsided by just how much more advanced Ford's new F-150 is compared to the current Chevy Silverado/GMC Sierra. GM's new trucks are still excellent choices, but its Ford rival is just light years ahead, especially in regards to fuel economy. GM has apparently accepted this fact, and now Reuters is reporting the US automaker has pushed forward the launch of its next-generation full-size pickups by about nine months to fall of 2018.
GM has so far not commented on this report, but the writing is on the wall: The General simply has no choice here. The full-size pickup truck market is too important to ignore. About a year after the new Silverado/Sierra twins arrive, GM will also launch its next-gen full-size SUVs, which will also go on diets. What's still unknown, however, is whether or not GM will make the switch to lightweight aluminum in the way Ford has. For its part, Ford has made clear it will continue to improve its new F-150 in the coming years, both in terms of new features and additional weight-saving measures.