As gasoline prices price skyrocketed in late 2007 and early 2008, GM’s truck engineering team was concerned about what would happen to their products, which had been providing a consistent flow of revenue to the automaker’s bottom line. Their worry was well-placed as the reality was worse than their expectations—GM’s light truck volumes fell 23% through the first seven months of 2008, and the company canceled the development of the next-generation full-size truck platform. It will rely on the existing GMT-900 as its workhorse for the foreseeable future.
“A couple of things happened that resulted in that decision: The fact is, the company has to devote so much money into powertrain technologies right now, and that is skimming some money right off the top. Then we realized that we could do more to the 900 to make it better as we stepped away from a total reliance on trucks for our profits,” says Gary White, GM North America vice president and vehicle line executive for full-size trucks.
Even before the next-generation truck was canceled, White and his team worked to respond to increased customer demands for greater fuel economy. Within six months, the team came up with the XFE (extra fuel economy) family of pickups and SUVs—limited to two-wheel-drive models equipped with the 5.3-liter V8 and 6-speed automatic transmission—achieving a 5% increase in EPA highway fuel economy and 7% in the city rating (15 MPG city/21 MPG highway versus 14 MPG city/20 MPG highway). “These changes were not in the original plan for the GMT-900,” says Jeff Luke, vehicle chief engineer for GM’s full-size trucks.
Engineers focused on borrowing from GM’s parts bin to reduce the weight of the XFE models by upwards of 150 lbs. The biggest contributor—accounting for 100 lbs.—was the decision to swap out the cast iron engine block for an aluminum one. Aluminum lower control arms and wheels—including the spare—also played significant roles. Engineers then focused on improved aerodynamics—the XFEs achieve a 0.412 Cd—by opting for the lower front air dam from the hybrid trucks and SUVs, lowering the suspension, and adding a soft tonneau cover to the pickup beds. Additional tweaking of the algorithms on the active fuel management system allows the engine to operate longer in 4-cyl. mode, providing added fuel economy benefits.
Surprisingly, the team passed on using the aluminum hood, liftgate and roof from the hybrid trucks to reduce mass. “We wanted to keep these as mainstream trucks and also wanted to keep some exclusivity for the hybrids so we decided not to use more aluminum of the XFEs,” says White. Cost was another big factor. Chief engineer Luke points out aluminum prices are rising faster than steel and that makes it more difficult to justify usage of the material at a time when profits are illusive. However, he remains confident aluminum will play a vital role in the quest to reduce vehicle weight.
Another critical factor was capability. Luke and his team wanted to make sure the XFEs did not skimp when it came to towing capacity. The Tahoe and Yukon XFEs maintain their existing tow rating, while the Silverado and Sierra pickups can tow an additional 400 lb. with the addition of a 6-speed automatic transmission and 3.08 ratio rear axle.
Unlike many prognosticators, White doesn’t believe the full-size truck segment is going to continue its dramatic pace of decline, expecting it to level off in the near-term before rebounding slightly when the U.S. economy begins to recover. “We’ve been talking to people who make trailers and boats and we found out that Sea Ray is not going to a strategy of making just canoes. People will still need the capabilities of a truck. Our goal is to find ways to make them more efficient without sacrificing capability, because we are not going to have unlimited funds to develop trucks anymore.”—KMK