Gearing Up Drive Axle Innovations

January 1, 2019

While electric and robotic cars tend to dominate the mainstream automotive news, SAE readers know the huge investments being made to improve “traditional” vehicle technologies — body structures, chassis and driveline systems, lightweight materials — for greater overall efficiencies, improved safety and reduced cost. Tier 1 driveline systems supplier American Axle & Manufacturing currently has Quantum, its all-new family of lightweight beam axles with aluminum center housing, in customer evaluations for future light trucks, crossovers and SUVs.

When AE learned there’s NASA technology inside the Quantum “pumpkin,” we asked Jeffrey Nichols, AAM’s executive director, advanced technology integration, to explain.

It’s our understanding that the new Quantum drive axle contains some trick aerospace technology, correct?

Architecturally Quantum is different than previous drive axle designs, most of which haven’t changed in over 100 years. Our design makes the drive module much more power-dense and compact. We’re able to achieve these gains because we eliminated a number of components. The traditional tapered roller bearings that you’d see on the pinions and differential are gone. In fact, the bearing races are now integrated with the pinion shaft. The pinion shaft serves multiple purposes.

Your company’s CTO, Phil Guys, told me in 2017 that Quantum axles have no shims.

That’s right — no shims. No spacers! It’s a net-build environment. The bearings are separated by ‘race dividers.’ We’re leveraging four-point bearing contact, and those bearings are rotating to meet the load requirements on demand. Some NASA bearing technology we studied inspired us to look at axle bearings a bit differently. That opened the space for our team to integrate the components that exist in that same space today.

At the time AAM was claiming some pretty big efficiency gains for this product.

Quantum has hundreds of thousands of miles that validate our analytical work to prove the technology. We’re hitting our target of up to 1.5 percent efficiency improvements, versus conventional RDAs [rear drive axles]. And the mass-reduction numbers — some exceeding 30 percent, or up to 100 pounds in a full-size pickup due to secondary-mass reductions that Quantum enables — are exciting our customers. The 1.5 percent improvement is quite significant in terms of vehicle fuel efficiency. And that is low-hanging fruit.

Do the new bearing technologies also provide NVH benefits?

Yes, the unique bearing arrangement and its four-point contact performance gives us the improved NVH behavior that AAM and our customers are looking for as well. Our testing and customer evaluations have shown Quantum doesn’t have the gear-whine issues of traditional axle designs. Our NVH profile is improved, but the axle itself is ‘transparent.’ At Winter Test, customers got into the vehicles with Quantum and couldn’t hear anything — that’s exactly what we want!

Can the aluminum center housing also be paired with aluminum tubes for live-axle applications? And does the Quantum design translate to an IRS?

Definitely steel tubes. And yes, the core architecture doesn’t change for independent rear suspensions. The application of split clutches for torque vectoring and biasing, we provide various ways to execute torque transfer. We can include axle-disconnect functionality, too. We’re also engaged with a customer for a Quantum front axle application.

Thermal management is critical in drive axles. What is AAM’s lubricant for Quantum?

Great question (laughs), but I can’t really get into lube specifics. I can say that it’s very unique and there are additives. We have a strong collaboration with our lubricant partner Lubrizol, who have been with us since the beginning of this program.

AAM’s new Quantum Driveline is the winner of the inaugural Lightweighting Innovation Award, sponsored by Ducker Worldwide and announced in late 2018 at the Society of Automotive Analysts (SAA) summit. Quantum’s combination of reduced mass with increased power density and improved NVH performance put it at the top of 15 finalists, according to the award judges.