Other Motor Vehicle Parts Manufacturing (United States)

NAICS 2022 code 33639 — an investor's primer (industry-group level)

1. Overview

This page covers NAICS 33639, one rung up the classification ladder from the detailed industry you may be looking for. The North American Industry Classification System (NAICS) is the coding scheme U.S., Canadian, and Mexican statisticians use to sort businesses; it nests like a set of Russian dolls, from broad two-digit sectors down to five- and six-digit industries. NAICS 33639 sits near the bottom of that ladder, and it is a special case: it contains exactly one child industry, 336390 — Other Motor Vehicle Parts Manufacturing. So this level and its child describe the same set of factories, workers, and shipments.

In plain terms, 33639/336390 is the "everything else" bin of the car-parts factory world — the makers of airbags and seatbelts, catalytic converters and exhaust systems, radiators and other cooling ("thermal management") parts, air-conditioning compressors, air filters, road wheels (the metal rims), windshield wipers, fuel tanks, and bumpers [4]. It is real, cash-generating manufacturing tied to one of the economy's largest end markets, and it sits squarely in today's crosscurrents: the shift to electric vehicles (EVs), tariffs, and precious-metal prices.

Because this level is a one-to-one pass-through, this is a short page. It states the level, gives our ground-truth federal figures for 33639, and points you to the full 336390 primer for the detail — the product families, the investable companies, the economics, and the risks.

2. What's inside — and why this level equals its one child

NAICS assigns a five-digit "industry" a distinct six-digit "national industry" code only when the United States needs to split it further. Here it does not: 33639 has a single U.S. industry beneath it, 336390, and the "0" simply signals "no further U.S. breakout." The two codes are therefore interchangeable — every establishment, dollar of shipments, and worker counted under 33639 is the same one counted under 336390.

What that single child covers, in brief [4]:

• Occupant safety / restraints — airbag assemblies and seatbelt systems
• Emissions and exhaust — catalytic converters, mufflers, resonators, exhaust systems
• Thermal / climate — radiators and cores, air-conditioning compressors and condensers
• Wheels — steel and aluminum road wheels (rims) for cars, trucks, and buses
• Miscellaneous — air filters, windshield wipers, bumpers, fuel tanks, frames, convertible tops, jacks

It deliberately excludes the parts that get their own codes — engines (336310), electrical/electronic gear (336320), steering and suspension (336330), brakes (336340), transmissions and power-train (336350), seating and interior (336360), and metal body stampings (336370). Tires (326211) and automotive glass (327215) sit outside the 3363xx family altogether [4]. 336390 is the residual "other" that catches what those seven do not — and because a large supplier such as Denso or Forvia makes products spanning several codes at once, no single code captures a whole company; 336390 counts only the qualifying establishments.

For all detail below the headline, read the child primer: 336390 — Other Motor Vehicle Parts Manufacturing.

3. How big it is (this level's rollup)

Because 33639 contains only 336390, its rollup figures are the child's figures. Our ground-truth federal numbers for NAICS 33639 in the United States:

That works out to roughly $50 million of shipments and about 109 workers per establishment, and an average wage near $57,700 [1][2] — mid-scale, capital-intensive factories rather than mom-and-pop shops. The Small Business Administration treats a firm here as "small" up to 1,000 employees, a high bar that reflects how equipment-heavy the work is [3].

Three caveats on the number. First, $66.5 billion is only one of eight motor-vehicle-parts codes; the full U.S. auto-parts manufacturing base across all 3363xx codes is several times larger [17]. Do not mistake this slice for the whole auto-parts industry. Second, this is not an industry badly undercounted by federal business statistics — its establishments are established firms that file, so the usual "small/individual-ownership undercount" is minimal here. The real distortion runs the other way: 33639 is a residual "other" bucket that blends genuinely different product markets (a wheel plant and an airbag plant have little in common), so any single industry-wide average blurs more than it reveals — and because many leaders are foreign-owned, the domestic data captures their U.S. plants but not the global company behind them. Third, NAICS is establishment-based and measures U.S. production, not U.S. consumption: exports are counted, imports are not, and adding shipment values across supplier tiers double-counts components embedded in other components.

4. The investable universe (where value concentrates)

With only one child, there is no "which sub-industry" question at this level — value concentrates by product line within 336390, not by code. There is no pure-play public company for the bucket; it is too broad. Investors assemble exposure by theme, and much of the industry is private or foreign-owned, so public markets show only a slice [5][6][7][8][9][10][11][12][13]. The child primer carries the full company table and ownership map; in short:

• U.S.-listed names with meaningful exposure: Autoliv (airbags and seatbelts; $10.8 billion of 2025 sales and roughly 44% of the global airbag and 45% of the seatbelt market) [5]; Modine (thermal management, about $2.6 billion in FY2025) [6]; Gentex (auto-dimming mirrors, roughly 79% global share — though its classification straddles 336390 and the excluded automotive-electronics code) [7]; Dorman and Standard Motor Products (aftermarket) [8][9]; Superior Industries (aluminum wheels, delisted from the NYSE in June 2025 and now over-the-counter) [10].
• Large private / foreign-owned players: Tenneco (Apollo-owned since November 2022; roughly $18 billion of revenue, 71,000 employees and more than 260 sites at the time of the buyout; exhaust and clean-air) [11]; Flex-N-Gate (bumpers and structures; more than 27,000 employees and 78 sites) [12]; global Tier-1s Denso, Forvia (€26.2 billion of 2025 group sales at a 5.6% operating margin) [13], Valeo, Mahle, Eberspächer and Hanon; airbag #2 Joyson [16]; wheel makers Maxion, Accuride and Ronal [19].

Two things to hold in mind at this level. Company revenue is global and spans several parts codes at once, so none of these figures is comparable to the $66.5 billion of U.S. shipments in Section 3 — do not add them up. And the private and foreign-owned side of the industry is the larger one, which is why private equity and private credit reach parts of this bucket that public markets do not. Tickers, valuation multiples, and yields belong with those specific names — see Section 4 and Section 10 of the 336390 primer.

5. How the money works

The economics are those of cyclical manufacturing: owners make money on volume, mix, and cost discipline. Two channels set the margin profile — thin, sticky OEM (original-equipment) sales to automakers for new vehicles, roughly two-thirds of parts demand by value [17], versus higher-margin, steadier aftermarket sales to repair the cars already on the road.

The single most useful thing the revised child research establishes is that there is no defensible "industry margin" at this level. Operating margins across the bucket's leaders run from about 19% at Gentex [7] and 10.1% at Autoliv [5] down to 5.6% at Forvia group level [13] and roughly 2.3% at Superior Industries, whose gross margin is just 8.7% [10] — while Dorman, which designs and sources rather than manufactures much of its catalog, earns a 42.1% gross and 14.1% operating margin but buys about 77% of its product outside the United States, 38% of it from China [8]. Averaging across a residual bucket that contains all of these is a category error.

The levers behind that spread are consistent, though. Capacity utilization is the profit dial (high fixed costs mean full plants are very profitable and idle ones bleed). Raw-material and precious-metal costs are largely passed through — Autoliv's direct materials were about 54% of 2025 sales [5], and Superior's contracts index aluminum, but the timing of customer price adjustments rarely matches the timing of cost changes, so pass-through smooths revenue more reliably than it smooths gross profit [10][18]. Customer power caps the upside: OEM programs typically run five to seven years with annual price give-backs written in, Autoliv's five largest customers were about 44% of 2025 sales and its ten largest about 70% [5], and General Motors, Ford, Volkswagen and Toyota alone were 24%, 16%, 12% and 12% of Superior's 2024 sales [10]. Content per vehicle — more airbags, bigger wheels, far more EV cooling hardware — is the main organic growth lever. Watch capacity utilization, OEM/aftermarket mix, margin net of metal pass-through, new-program awards, and free cash flow versus debt. Full detail is in Section 5 of the child primer.

6. What drives demand

• The auto cycle — OEM parts demand tracks new-vehicle production. U.S. automobile and light-truck assemblies averaged a seasonally adjusted annual rate of about 10.0 million in 2025 against 10.2 million in 2024 [20], while U.S. new-vehicle registrations topped 16 million in 2024 for the first time since 2019 [15].
• The installed base — about 289 million vehicles in operation at a record average age of 12.8 years feed a large, stable aftermarket that grows regardless of new-car sales [15].
• Rising content per vehicle — safety rules, bigger wheels, and electrification push more of this bucket's dollars into each car.
• Electrification, a two-sided force — EVs erase the tailpipe (exhaust, mufflers, catalytic converters and fuel tanks decline roughly –3% a year through 2030, accelerating toward –8% by 2035) but add battery and power-electronics cooling, so thermal management grows [21]. The transition is material but neither linear nor complete: EVs were 9.4% of U.S. new light-vehicle sales in 2025, down from 9.8% in 2024 [22] — which is why the child primer treats stranding risk and pivot risk as live in both directions.
• Trade policy — tariffs reshape where parts are sourced (Section 7).

7. Regulation

Regulation is unusually load-bearing because several of these products exist because the law requires them. Airbags and seatbelts are mandated by the National Highway Traffic Safety Administration (NHTSA) under Federal Motor Vehicle Safety Standard (FMVSS) 208, whose defect-reporting regime also creates recall and remedy exposure for the equipment maker [4][16][23]. Catalytic converters exist to meet Clean Air Act limits enforced by the Environmental Protection Agency (EPA) and California's Air Resources Board (CARB), with removal treated as illegal "tampering" and 2025 enforcement pursuing fines of up to $50,000 per vehicle [24]; converter theft has drawn federal marking-and-traceability proposals [24]. Note that regulatory reversals cut both ways: EPA's February 2026 rescission of federal motor-vehicle greenhouse-gas standards expressly left traditional air-pollutant rules — the ones that create the converter — untouched [25], so the demand case for emissions hardware rests on those, not on climate rules.

Separately, 2025's Section 232 tariffs (25% on imported autos and many parts, effective May 3, 2025) push production toward North America while raising costs for import-reliant suppliers [26]. USMCA-qualifying parts are largely exempt, and qualification turns on regional value content — 75% for passenger vehicles and light trucks, 70% for principal parts, and 65% for complementary parts including catalytic converters [27]. The cost pressure is broad: in a March 2025 survey of 139 suppliers, more than 80% reported exposure to steel or aluminum derivative tariffs and more than a third were exposed through both imported inputs and delivered products [28], and Gentex disclosed that unrecovered tariffs cut its 2025 gross margin by about 110 basis points [7]. Safety parts also carry catastrophic recall risk — the Takata airbag-inflator recall, the largest in history, is the permanent reminder. See Section 7 of the child primer for the full picture.

8. Consolidation

Federal data make the level look fragmented — the top four firms hold just 13.6% of receipts and the Herfindahl-Hirschman Index (HHI, a concentration gauge where under 1,500 is "unconcentrated") is a very low 125.4 [2]:

But that low number is an artifact of the "other" bucket lumping unrelated products together. Within each real product market, concentration is high: airbags and seatbelts are an oligopoly (Autoliv, at roughly 44% of the global airbag market, plus Joyson and ZF) [5][16]; exhaust and clean-air are led by Forvia, Tenneco, and Eberspächer [29]; wheels by Maxion, Superior, Accuride, and Ronal [19]. The industry is "fragmented in aggregate, concentrated in the aisle you actually shop," and consolidation — automakers favoring fewer, larger, better-capitalized Tier-1 partners — is the through-line. It is financed well (Apollo taking Tenneco private [11]; Standard Motor Products buying Europe's Nissens engine-cooling business for about $390 million in 2024 to widen its temperature-control line [9]) and badly (First Brands' leveraged aftermarket roll-up collapsing into 2025 bankruptcy with more than $10 billion of liabilities, and fraud charges against its executives [14]).

9. Risks

The child-level risks apply unchanged at this level: cyclicality (OEM revenue swings with vehicle production), customer power and concentration (a few automakers buy most OEM output and extract annual price cuts [5][10]), electrification stranding (exhaust and converter lines in permanent decline [21]), commodity and platinum-group-metal volatility (rhodium traded above $11,000 an ounce in 2026, inflating working capital and inviting converter theft [18]), leverage (debt-heavy private-equity structures — First Brands is the cautionary tale [14]), tariffs and supply-chain shocks [26][28], and the recall/liability tail on safety-critical parts. The revised child adds one more that is worth carrying up: capital allocation under an uncertain transition — funding new EV programs while maintaining legacy internal-combustion capacity depresses returns whether electrification arrives faster or slower than planned, and the 2025 dip in U.S. EV share [22] shows the timing is genuinely unsettled. Section 9 of the 336390 primer expands each.

10. How to invest, and the outlook

There is no single ticker for this level; public-market investors build exposure by theme — safety and secular content growth (Autoliv, largely insulated from the EV-versus-combustion debate because every vehicle needs restraints) [5][16], EV and data-center thermal (Modine) [6], higher-margin vision systems (Gentex) [7], aftermarket resilience geared to the aging fleet rather than the new-car cycle (Dorman, Standard Motor Products) [8][9], or deep-cyclical turnaround (Superior Industries, now over-the-counter and highly leveraged — a distressed situation, not a core holding) [10]. Broad auto-supplier and industrial ETFs give only indirect exposure; most hold automakers, semiconductor companies and technology vendors rather than anything resembling pure 336390. Because most of the industry is private, it is also fertile ground for private equity (aftermarket and Tier-2 roll-ups, and — as Apollo's Tenneco deal showed — whole global suppliers) and private credit (lending to those platforms), alongside enduring family- and founder-controlled suppliers such as Flex-N-Gate [11][12][14]. Diligence there turns on program-level profitability, customer recovery mechanisms, tooling ownership, environmental and pension liabilities, recall indemnities, and how much capital a new program burns before it turns cash-positive — First Brands is the live warning that capital structure and disclosure quality matter as much as the parts.

The base case is a large, mature industry growing slowly in aggregate but bifurcating underneath: a firm aftermarket underpinned by a record-old, 289-million-vehicle fleet [15], a structural loser in internal-combustion exhaust and converters [21], a structural winner in thermal management, and tariffs nudging production toward North America while raising costs for import-dependent suppliers [26]. The durable lesson is that "auto parts" is not one bet — the sub-segment, the OEM/aftermarket mix, and the balance sheet decide the outcome far more than the sector label.

Bottom line: 33639 and 336390 are the same industry. For the full company table, valuation guidance, and detailed analysis, read the leaf primer — 336390, Other Motor Vehicle Parts Manufacturing.

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Sources

Drawn from the child primer (NAICS 336390). Figures in Sections 3 and 8 are our ground-truth federal statistics for NAICS 33639.

1. U.S. Census Bureau, County Business Patterns, 2023 (NAICS 336390: establishments, employment, annual payroll). https://www.census.gov/programs-surveys/cbp.html
2. U.S. Census Bureau, 2022 Economic Census — Industry Statistics and Concentration (NAICS 336390: receipts, firms, CR4/CR8/CR20/CR50, HHI). https://www.census.gov/programs-surveys/economic-census.html
3. U.S. Small Business Administration, Table of Small Business Size Standards, 2023 (NAICS 336390: 1,000 employees). https://www.sba.gov/document/support-table-size-standards
4. NAICS Association, "NAICS Code 336390 — Other Motor Vehicle Parts Manufacturing" (industry definition, product examples, cross-references), 2024. https://www.naics.com/naics-code-description/?code=336390
5. Autoliv, Inc., 2025 Form 10-K (sales $10.815 billion; 10.1% operating margin; ~44% airbag and ~45% seatbelt global share; direct materials ~54% of sales; customer concentration; contract duration; product-liability disclosure). https://www.sec.gov/Archives/edgar/data/1034670/000119312526058162/alv-20251231.htm
6. Modine Manufacturing Co., FY2025 results — record net sales of $2.6 billion (Form 8-K, 2025). https://www.sec.gov/Archives/edgar/data/67347/000155837025008029/tmb-20250520xex99d1.htm
7. Gentex Corporation, 2025 Form 10-K (sales $2.534 billion; ~19% operating margin; 79% auto-dimming mirror share; unrecovered tariff impact ~110 bps). https://www.sec.gov/Archives/edgar/data/355811/000035581126000010/gntx-20251231.htm
8. Dorman Products, Inc., 2025 Form 10-K (sales $2.130 billion; 42.1% gross margin; 14.1% operating margin; 77% of purchases from outside U.S., 38% from China). https://www.sec.gov/Archives/edgar/data/868780/000086878026000014/dorm-20251231.htm
9. Standard Motor Products, Inc., "Fourth Quarter and 2024 Year-End Results" (net sales $1.46 billion) and "SMP Completes Acquisition of Nissens Automotive" (~$390 million), 2024–2025. https://www.smpcorp.com/newsroom/financial/smp-releases-fourth-quarter-and-2024-year-end-results/
10. Superior Industries International, Inc., FY2024 Form 10-K (revenue $1.267 billion; 8.7% gross margin; ~92% OE aluminum wheels; customer concentration; pass-through timing) and "Superior Industries International Receives NYSE Delisting Notice" (Businesswire, June 2025). https://www.sec.gov/Archives/edgar/data/95552/000095017025034599/sup-20241231.htm
11. Tenneco Inc. / Apollo Global Management, acquisition completion announcement (November 2022; 2021 revenue ~$18 billion; 71,000 employees; 260+ sites). https://www.sec.gov/Archives/edgar/data/1024725/000119312522287303/d190359dex991.htm
12. Flex-N-Gate, corporate profile (27,000+ employees; 78 facilities). https://flex-n-gate.com/our-group/
13. FORVIA, 2025 Annual Results (sales €26.2 billion; 5.6% operating margin). https://www.forvia.com/en/press/2025-annual-results
14. U.S. Department of Justice, "First Brands Executives Charged With Multibillion-Dollar Fraud" (2026), and Transport Topics, "Auto Parts Maker First Brands Files for Bankruptcy" (Chapter 11, September 2025; >$10 billion liabilities). https://www.justice.gov/usao-sdny/pr/first-brands-executives-charged-multibillion-dollar-fraud
15. S&P Global Mobility, "U.S. Vehicle Age Rises Again to 12.8 Years in 2025" (289 million vehicles in operation; >16 million registrations in 2024), May 21, 2025. https://press.spglobal.com/2025-05-21-U-S-Vehicle-Age-Rises-Again-to-12-8-Years-in-2025,-According-to-S-P-Global-Mobility
16. Mordor Intelligence and The Business Research Company, automotive airbags-and-seatbelts market reports (market ~$52.5 billion in 2024; key players Autoliv, Joyson Safety Systems, ZF), 2024–2025. https://www.mordorintelligence.com/industry-reports/automotive-airbags-and-seatbelts-market
17. Grand View Research / Mordor Intelligence, U.S. auto-parts and aftermarket market sizing (OEM channel roughly two-thirds of parts value; total U.S. auto-parts output far larger than any single NAICS sub-code), 2025. https://www.grandviewresearch.com/industry-analysis/aftermarket-automotive-parts-market
18. PMR and Recohub, catalytic-converter precious-metal content and pricing analyses (platinum, palladium, rhodium content; rhodium >$11,000/oz in 2026), 2025–2026. https://pmrcc.com/en/news-blog/catalytic-converter-101/catalytic-converter-value/
19. GlobeNewswire, "Automotive Wheels Aftermarket … Maxion Wheels, Accuride Corp, and Ronal Group Lead" and "Alloy Wheels Aftermarket … Superior Industries Int'l," September 2025. https://www.globenewswire.com/news-release/2025/09/19/3153329/0/en/
20. Federal Reserve Bank of St. Louis (FRED), U.S. Motor Vehicle Assemblies (seasonally adjusted annual rate, 2024–2025). https://fred.stlouisfed.org/graph/?g=1PwAf
21. MarketsandMarkets and GMInsights, automotive exhaust-system market analyses (structural decline of ICE exhaust/catalytic converters, ~–3% to –8% CAGR; growth in EV thermal management), 2025; BCG, "2026 Global Automotive Supplier Study." https://www.marketsandmarkets.com/Market-Reports/automotive-exhaust-system-market-87800437.html
22. Alliance for Automotive Innovation, "Get Connected — Electric Vehicle Sales Dashboard" (U.S. EV share 9.4% in 2025, down from 9.8% in 2024), January 2026. https://www.autosinnovate.org/posts/papers-reports/stay-connected1-30-2026
23. National Highway Traffic Safety Administration (NHTSA), manufacturer guidance and defect-reporting requirements. https://www.nhtsa.gov/vehicle-manufacturers
24. Congressional Research Service, "Addressing Catalytic Converter Theft" (IF11870) and EPA Clean Air Act anti-tampering enforcement (fines up to $50,000/vehicle, 2025); CARB aftermarket-converter certification. https://www.congress.gov/crs_external_products/IF/PDF/IF11870/IF11870.2.pdf
25. U.S. Environmental Protection Agency, Final Rule: Rescission of Greenhouse Gas Endangerment (February 2026; traditional air-pollutant rules unaffected). https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-rescission-greenhouse-gas-endangerment
26. Congressional Research Service, "Section 232 Automotive Tariffs: Issues for Congress" (2025), and Federal Register, "Adjusting Imports of Automobiles and Automobile Parts" (25% parts tariff effective May 3, 2025; USMCA treatment). https://www.congress.gov/crs-product/IN12545
27. Office of the United States Trade Representative, USMCA automotive rules summary (75% regional value content for vehicles; 70% principal parts; 65% complementary parts). https://ustr.gov/sites/default/files/files/Press/Releases/USTR%20USMCA%20Autos%20White%20Paper.pdf
28. Motor & Equipment Manufacturers Association (MEMA), tariff survey (March 2025; 139 suppliers; >80% exposed to steel or aluminum derivative tariffs). https://www.mema.org/news/mema-statement-ongoing-impact-steel-and-aluminum-tariffs
29. MarketsandMarkets, "Automotive Exhaust System Market — Leading Players" (Forvia, Tenneco, Eberspächer, Friedrich Boysen), 2025. https://www.marketsandmarkets.com/ResearchInsight/automotive-exhaust-system-market.asp