Advanced Materials and Forging Technology Help Reduce Mass and Rotational Inertia in Drive Shaft Flange

Detroit, MI, May 25, 2005 –By combining advanced materials technology with advanced forging technology, IMPACT (Improved Materials and Powertrain Architectures for 21st Century Trucks) team engineers at Ford Motor Company reduced stationary mass in a transmission drive shaft flange by 2.18 lbs., or 34 percent, while rotational inertia went from 21.49 in 2-lbs. to 9.47 in 2-lbs. (56 percent reduction). The application is in Ford’s 250/350 Pickup Trucks and is part of the IMPACT Project sponsored by the U.S. Department of Defense (DoD). The redesign involved changing from cast iron to a forged microalloy steel flange.

Material Properties


Cast Iron


Tensile Strength

100 ksi

130 ksi

Yield Strength

70 ksi

110 ksi




David Anderson, director, Long Products Programs, American Iron and Steel Institute (AISI), reports that the substitution of a higher strength, more formable material permitted the following design benefits:

  • Reduced flange diameter by 2.5mm
  • Increased fillet to 6mm
  • Lobes instead of constant diameter
  • Reduced thickness to 10mm

The switch from a casting to a forging eliminates a significant amount of machining (Figure 1). The casting was machined 100 percent, while the forging results in a near-net-shape part that requires machining of only both end faces, the mounting holes, and the spline shaft. The controlled cooling from forging temperature, which is part of the new technology in forging, eliminates subsequent thermal treatment. Through the material saving and the reduced machining, the cost of the new design is actually less than the cost of the cast part.

Figure 1 – Redesign of the Output Hub

Anderson is quick to point out, “We do not recommend redesign for mass reduction on a part-by-part basis. Instead, we firmly believe in the clean-sheet design approach demonstrated by the UltraLight Steel Auto Body (ULSAB) project.”

“The IMPACT Project, however, is a total vehicle redesign, which is about as close as most automakers can get to clean-sheet-design for an existing platform,” said Anderson. “The transmission output hub cited in this example is just one of many powertrain components for which significant optimization was achieved.”


The IMPACT project focus is designing, incorporating and validating fuel efficient, lightweight technologies in demonstration vehicles of next generation, high-volume, commercially based truck platforms. Partners in the IMPACT Project are Ford Motor Company, U.S. Army Tank Automotive and Armament Command (TACOM), American Iron and Steel Institute, Mississippi State University, University of Louisville and Oak Ridge National Laboratory.

The DoD sponsored the IMPACT project to develop strategies for reducing weight, enhancing performance, improving mobility and increasing fuel economy of tactical trucks for the U.S. Army. The modern military requires a more agile vehicle fleet that is lighter, more affordable and quickly deployable anywhere in the world. IMPACT is part of the DoD’s Dual Use Science and Technology (DUST) program, in which industrial partners such as Ford Motor Company, the government and academia leverage resources to optimize technologies that have potential applications in both military and commercial vehicles (dual use). In addition to government financial support, Ford Motor Company and the AISI contributed to the funding of IMPACT.

In addition to funds, AISI provided in-kind services (engineering, technology, ULSAB consortium study information, etc.), steel materials for prototypes, specific soft tool funds and component prototypes. The project started in 1999 and concluded in 2002.

Additional details of the IMPACT Project will be available as they are released by Ford Motor Company and TACOM.