# American Axle v. Neapco: When a Natural Law Sank a Manufacturing Patent

> The Federal Circuit held a driveshaft manufacturing method ineligible under Section 101 for invoking Hooke's law, pushing Mayo deep into the mechanical arts.

Topic: Patents  |  Author: Lidiia Levitska  |  Source: Intellectual Property Law (outsideipcounsel.com)
Canonical: https://outsideipcounsel.com/blog/american-axle-v-neapco-natural-law-manufacturing/


*American Axle & Manufacturing, Inc. v. Neapco Holdings LLC*, 967 F.3d 1285 (Fed. Cir. 2020), is the decision that made patent lawyers realize the natural-law exception to Section 101 was no longer confined to diagnostics and software. In a case about the mundane business of building vehicle driveshafts, a divided Federal Circuit held that a method of manufacturing a driveline propeller shaft was ineligible for patenting because, at bottom, it claimed nothing more than an application of Hooke's law. The ruling extended the Supreme Court's framework from *Mayo Collaborative Services v. Prometheus Laboratories, Inc.*, 566 U.S. 66 (2012), into the heart of the mechanical arts, and the resulting 6-6 en banc split and eventual denial of certiorari turned the case into the rallying point for a decade of eligibility reform proposals.

## At a glance

- **Case:** *American Axle & Manufacturing, Inc. v. Neapco Holdings LLC*, 967 F.3d 1285 (Fed. Cir. 2020)
- **Court:** United States Court of Appeals for the Federal Circuit
- **Decided:** Modified opinion issued July 31, 2020, alongside a 6-6 denial of en banc rehearing; certiorari denied June 30, 2022
- **Holding:** Method claims for manufacturing a driveshaft with a tuned vibration-damping liner are patent-ineligible under 35 U.S.C. Section 101 because they are directed to the application of a natural law (Hooke's law) without a sufficient inventive concept
- **Status:** Final. Binding Federal Circuit precedent as of July 2026.

## The technology and the claims

American Axle's U.S. Patent No. 7,774,911 addressed a real engineering problem. Driveshafts in cars and trucks transmit torque from the transmission to the wheels, and they vibrate in several distinct modes at once: bending vibration (the shaft flexing along its length), torsion vibration (twisting), and shell-mode vibration (the tube wall deforming). Manufacturers had long inserted liners into hollow propshafts to absorb some of this energy, but a given liner typically addressed only one vibration mode.

The '911 patent described inserting a liner "tuned" to damp more than one mode simultaneously. Claim 22, the claim the court ultimately held ineligible, recited providing a hollow shaft member, "tuning a mass and a stiffness of at least one liner," and "inserting the at least one liner into the shaft member," with wherein clauses requiring that the liner serve as a tuned resistive absorber for shell-mode vibration and a tuned reactive absorber for bending-mode vibration. Independent claim 1 was worded differently: it required "tuning at least one liner to attenuate at least two types of vibration" and then "positioning" the liner within the shaft member. That wording gap mattered to the outcome. The dispute turned on what the claims actually taught. Neapco argued, and the majority agreed, that the claims recited the desired result (a liner tuned to attenuate two modes) without disclosing the specific means of achieving it. The concept of "tuning," the court found, was simply the application of Hooke's law, F = kx, which relates the force in a spring to its stiffness and displacement, together with known principles of friction damping.

## The Mayo framework reaches the mechanical arts

To appreciate the shock of *American Axle*, one has to see where the doctrine stood. Section 101 says nothing about laws of nature on its face. The exclusion for laws of nature, natural phenomena, and abstract ideas is a judge-made gloss, and a claim falls outside eligibility only if it is "directed to" one of those concepts. The Supreme Court built the modern test in *Mayo* and *Alice Corp. v. CLS Bank International*, 573 U.S. 208 (2014): step one asks whether a claim is directed to one of those excluded concepts, and step two asks whether the claim adds an "inventive concept" that amounts to significantly more than the concept itself. Practitioners had largely understood that framework to police diagnostic correlations (as in *Mayo*), isolated natural products (as in *Association for Molecular Pathology v. Myriad Genetics, Inc.*, 569 U.S. 576 (2013)), and computer-implemented abstractions (as in *Alice*). Traditional manufacturing methods felt safe.

Writing for the majority, Judge Dyk rejected that comfort. The court held that a claim can be "directed to" a natural law even in a field that does not sound in biology or software, if the claim's advance lies in the invocation of that law rather than in a specific, disclosed technique for exploiting it. Because the claims required "tuning" a liner to hit a target frequency but did not teach how to design or construct such a liner beyond leaving the artisan to apply Hooke's law through trial and error, the majority concluded at step one that the claims were directed to the natural law itself. At step two, the recited steps of providing a hollow shaft and inserting a liner were conventional, adding no inventive concept. The claims therefore failed.

## The "Nothing More" problem and the enablement overlap

The most cited feature of the majority's reasoning is what Judge Moore's dissent named, and commentators then adopted, the "Nothing More" test. The majority framed its step-one holding as extending "only where, as here, a claim on its face clearly invokes a natural law, and nothing more, to achieve a claimed result." This framing drew immediate criticism for collapsing the eligibility inquiry into what looks like an enablement or written-description problem under 35 U.S.C. Section 112. If the objection is that the patent claims a result without teaching how to achieve it, that is classically a Section 112 defect, not a Section 101 defect. By routing a failure-to-teach concern through eligibility, the majority appeared to many observers to blur two distinct statutory requirements, importing "how to" scrutiny into a threshold that is supposed to ask only "what kind of thing" is claimed.

The panel had originally issued a broader opinion on October 3, 2019 that held all of the asserted claims ineligible and leaned on friction damping as a second natural law alongside Hooke's law. American Axle petitioned for panel rehearing, and on July 31, 2020 the court reissued a modified opinion that narrowed the result. It affirmed ineligibility as to claim 22, the claims depending from it, and claim 36, but vacated and remanded as to claim 1 and its dependent claims: because claim 1 adds a "positioning" step and may reflect a broader notion of "tuning" than the mass-and-stiffness control recited in claim 22, the court could not say claim 1 was directed to Hooke's law alone and left that question to the district court in the first instance.

## A court at war with itself

Judge Moore, later the court's chief judge, dissented from the panel opinion itself. She accused the majority of having imbued Section 101 with a new superpower that she called "enablement on steroids," and closed by warning that "the unfairness, confusion and uncertainty that will be caused by this opinion is all us."

The same day the modified opinion issued, the court denied rehearing en banc by an evenly divided 6-6 vote, so the panel opinion stood. *American Axle & Manufacturing, Inc. v. Neapco Holdings LLC*, 966 F.3d 1347 (Fed. Cir. 2020). Judges Dyk and Chen wrote separately in support of denial. Judges Newman, Stoll, and O'Malley each wrote dissents from the denial, joined in various combinations by one another and by Judges Moore and Reyna, and Judge Lourie dissented without opinion. Judge Newman wrote that the court's eligibility rulings "have become so diverse and unpredictable as to have a serious effect on the innovation incentive in all fields of technology." The fracture mattered because it signaled that eligibility law had become unpredictable even to the specialized court charged with administering it.

American Axle petitioned for certiorari. The Supreme Court, in an unusual step, called for the views of the Solicitor General. The government's brief agreed that the law was in disarray and urged the Court to grant review. Even so, on June 30, 2022, the Court denied certiorari, leaving *American Axle* on the books and leaving the Section 101 fault lines exactly where the Federal Circuit had left them.

## Open questions

*American Axle* resolved the fate of one driveshaft patent but unsettled far more than it decided. When is a claim "directed to" a natural law as opposed to merely relying on one, given that every mechanical invention operates within the laws of physics? How far does the "Nothing More" framing extend before it swallows any process defined partly by its objective? And where, precisely, is the line between a Section 101 eligibility defect and a Section 112 enablement defect when the complaint is that a claim recites a result without a mechanism? The court gave no administrable answer, and the denial of certiorari means these questions persist. Legislative fixes, including the proposed Patent Eligibility Restoration Act, have circulated in Congress in response, but as of July 2026 no statute has displaced the judicial framework.

## Implications for inventors and businesses

- **Disclose the mechanism, not just the goal.** Claims that recite a desired physical result achieved by "tuning," "configuring," or "optimizing" a parameter are vulnerable if the specification leaves the how-to to the reader's application of known physics. Draft to a specific technique, structure, or algorithm.
- **Eligibility risk is no longer field-specific.** Mechanical and manufacturing patents cannot assume immunity from Section 101. Any process whose novelty can be characterized as the application of a scientific principle is exposed.
- **Section 112 and Section 101 now overlap in practice.** Prosecutors should anticipate that an enablement weakness may resurface as an eligibility attack, and should build the specification to defeat both.
- **Track the reform debate.** Because *American Axle* survives, legislative or Supreme Court intervention remains the only path to a cleaner rule. Businesses with eligibility-sensitive portfolios should monitor developments and, where possible, pursue claims that emphasize concrete structural or algorithmic advances.

## Frequently asked questions

**What did American Axle's patent claim?** U.S. Patent No. 7,774,911 claimed a method of manufacturing a driveline propeller shaft by inserting a tuned liner that attenuates two kinds of vibration at once. The Federal Circuit read the claims as reciting the goal of tuning without disclosing how to achieve it beyond invoking a natural law.

**Why is the decision so controversial?** It extended the Mayo/Alice natural-law exception from diagnostics and software into a traditional mechanical manufacturing process. Critics, including several Federal Circuit judges, warned that almost any process could be recast as an application of physics, making the ruling a flashpoint in the Section 101 reform debate.

**Did the Supreme Court take up the case?** No. Despite inviting the Solicitor General's views, and despite the government urging review, the Supreme Court denied certiorari on June 30, 2022. American Axle remains binding Federal Circuit precedent as of July 2026.

## Authorities and sources

- *American Axle & Manufacturing, Inc. v. Neapco Holdings LLC*, 967 F.3d 1285 (Fed. Cir. 2020) (modified opinion). [Slip opinion PDF, Federal Circuit](https://www.cafc.uscourts.gov/opinions-orders/18-1763.opinion.7-31-2020_1628791.pdf); full text via [BitLaw](https://www.bitlaw.com/source/cases/patent/American-Axle.html).
- *American Axle & Manufacturing, Inc. v. Neapco Holdings LLC*, 966 F.3d 1347 (Fed. Cir. 2020) (order denying rehearing en banc, 6-6). [Order PDF, Federal Circuit](https://www.cafc.uscourts.gov/opinions-orders/18-1763.order.7-31-2020_1628780.pdf); full text via [BitLaw](https://www.bitlaw.com/source/cases/patent/American-Axle-En-Banc.html).
- U.S. Patent No. 7,774,911, "Method for attenuating driveline vibrations" (issued Aug. 17, 2010).
- 35 U.S.C. [Section 101](https://www.law.cornell.edu/uscode/text/35/101) (patent-eligible subject matter); 35 U.S.C. [Section 112](https://www.law.cornell.edu/uscode/text/35/112) (written description and enablement).
- *Mayo Collaborative Services v. Prometheus Laboratories, Inc.*, 566 U.S. 66 (2012), and *Alice Corp. v. CLS Bank International*, 573 U.S. 208 (2014).
- Quinn Emanuel, ["Update on Section 101 Patent Eligibility Law: American Axle and the Patent Eligibility Restoration Act"](https://www.quinnemanuel.com/the-firm/publications/noted-with-interest-update-on-section-101-patent-eligibility-law-american-axle-and-the-patent-eligibility-restoration-act/).
- Baker Botts, ["Revisiting American Axle: District Court Application of the Controversial Case"](https://www.bakerbotts.com/thought-leadership/publications/2022/june/revisiting-american-axle-district-court-application-of-the-controversial-case).
- Mintz, ["SCOTUS Declines to Answer Calls for Clarification in American Axle v. Neapco"](https://www.mintz.com/insights-center/viewpoints/2231/2022-07-13-scotus-declines-answer-calls-clarification-american-axle) (cert. denied June 30, 2022).