The Devil is in the Details for Lightweighting

The aluminum F-150 increased anxiety levels at GM and FCA, but the Chevy Silverado and Ram 1500 engineering teams responded with mixed materials and detail engineering for their new vehicles.

The 2013 unveiling of the Ford Atlas concept at the Detroit auto show sent shivers down the spines of the competition. It meant that, two years later, a 700-lb. lighter, aluminum-bodied F-150 would be hitting the market. Early planning for the next generation Silverado and Ram was just starting, and Ford had thrown them an unexpected curve with the switch from steel.

Lightweighting was already part of the agenda. The coming F-150 made it the main focus.
Mention this to Rob Wichman, head of all Ram engineering and Vehicle Line Executive, Ram, and his eyebrows arch as he recounts: “When Ford went with aluminum, we had to stop what we were doing and take a long look. We had to ask ourselves if they knew something we didn’t.” The same was true at GM where Scott Damman, Lead Development Engineer, Silverado recalls: “It was a bit of a surprise, really, especially considering all of the changes that decision brought downstream. GM had committed itself to a mixed-materials strategy, but we had to look and see if Ford was on to something. If anything, it caused us to work harder to maximize the gains that could be made using our strategy.”

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Slimming the Silverado
“Our executive chief engineer likes to say that there’s more than one material on the period table,” says Damman in a not-so-subtle jab at Ford. By hydroforming the frame rails out of high-strength steel, the engineers were able to create comprehensively boxed sections for stiffness that had varying thickness along its length and width. “This meant we were able to pull 80 pounds out of the frame while increasing its stiffness,” says Damman.

Another 80  pounds came out of the body, but it took more than swapping the closure panels—doors, hood and tailgate—over to aluminum. The program moved away from a one-piece body side to one that mixes high-strength and ultra-high-strength steel, revised the roll-formed steel bed and added optimized lightweight braces that allowed thinner-gauge sheetmetal to be used. The bed, in particular, was an area of concentration for the engineering team. Instead of stamping the bed in one piece, says Damman, “We make the wheelwells in one stamping, and weld them to the bed where they are later seam sealed.” This change has three major benefits: 1) It allowed the engineering team to specify a thinner, lighter, stronger steel for the bed floor, 2) A tighter radius could be used on the wheelwell blanks without cracking, and 3) Cargo bed space was increased.

It didn’t stop there. The rear suspension’s second-stage spring was switched from steel to a composite leaf spring, thanks to a proprietary technology that allowed a spring of this construction to live in a truck environment. Cast aluminum was specified for the front suspension’s upper control arms, replacing the stamped steel component found on the previous generation Silverado. Even the seats are slightly skinnier than before to reduce weight and increase interior room. Says Damman: “Every single design engineer was tasked with trying to find ways to reduce weight, and—since we were designing and building it from the ground up—we had the opportunity to look at areas we normally wouldn’t have to remove weight.” This detail focus also resulted in adding three inches to the length of the crew cab, slightly increasing the wheelbase, shortening the hood by moving the front wheels forward and adding an inch to bed length, all while increasing overall length by little more than an inch.

“Some of that extra room,” he says, “came from changing materials and parts to reduce weight and brought benefits we hadn’t expected when we started this project, like removing weight from the nose of the truck by altering the wheelbase and fighting to take out grams from components without affecting reliability.”

Reducing the Ram
Attention to detail also was central to the development of the 2019 Ram 1500, though—unlike Chevrolet, which claims a 450-pound weight reduction for the 2019 Silverado crew cab compared to a comparably equipped previous generation model—Ram is claiming just 225 pounds. “We had better things to do with our time than figure out what the outgoing Ram would have weighed with all the new equipment,” jokes Ram 1500 Chief Engineer Mike Raymond.

According to Ram engineering chief Wichman, “We took 100 pounds out of the frame by combining 96 ksi multi-phase high-strength steel with 30-85 ksi high-strength steel, 65 ksi advanced high-strength steel, variable thickness high-strength steel and some aluminum.” To which Raymond quickly adds: “We were able to downgauge by increasing the cross section of the frame rails, and evenly distribute the weight reduction along the length so that weight distribution across the frame wasn’t affected. It’s fully boxed and seam welded, as you’d expect, and we’ve increased its capability in terms of refinement, towing and cargo.”

Move rearward from the mandrel-formed, octagonal, splayed crush beams, and the weight savings continues. “We did use aluminum in some key areas,” says Wichman, “like the transmission crossmember, and the 6000 series beam that connects the lower control arms.”

The aluminum lower control arms were pretty much carried over, but the upper control arms are a new material and design. “This is more than a stamped-steel control arm,” says Raymond. “The void underneath is filled with a structural nylon insert, and the final part is both lighter and stronger than the aluminum part it replaces.”

On most every model (except for the Rebel, which uses Bilstein dampers), Hitachi supplies aluminum-body shocks that eliminate a total of two pounds. The exhaust system is nine pounds lighter by replacing the steel mounts with ones made from aluminum. Replacing the mechanical parking brake with an electrically actuated unit eliminated the cables and brackets, as well as the need for a separate, manually actuated brake unit. Combined, this reduced weight by 20 pounds. “It’s all detail engineering,” says Wichman. “Almost every component has dropped weight. We spent many weekends going through everything to make sure we hit the weight targets, and to make certain we could do more with less weight.”

Much like the 2019 Silverado, the Ram 1500’s crew cab is four inches longer—an inch in each door and two inches in the C-pillar—but the vehicle also is four inches longer overall. The doors are made of steel to keep repair costs down, while the hood and tailgate are aluminum. “Our D-pillar at the front of the box is hydroformed, creates a continuous section from side-to-side, and saves nine pounds,” says Wichman. “Plus, our bodyside apertures are still one piece. with both the door rings and cross-car beams made from hot-stamped steel.” Taken together, says Raymond, “the total weight reduction for cab and body together is 225 pounds.”

Ford’s 2015 F-150 was both a shock and a call to arms for the Silverado and Ram engineering teams. Unwilling to take on the higher costs necessary to produce an aluminum-intensive vehicle, or the downstream headaches of service and repair, they took a clean-sheet approach that combined a number of materials with a sharp focus on removing every available gram from the structure and components. For them, the devil truly was in the details.