In 2022 we published what was then and still is a heat treatment industry exclusive-a list of the “10 Largest Single Location Captive Heat Treats in North America”. We have continued this tradition and are proud to present what is now the “15 Largest Single Location North American Captive Heat Treats 2026”. However, before we do, we would like to explain our criteria and add some thoughts about this year’s list;

• Our criteria are simple in that this list only includes single locations and not total heat-treating capacity in North America. As an example, the “ZF Transmission” facility in South Carolina makes this list but overall, this plant is only a small percentage of the heat-treating capacity ZF has in North America.
• Our estimates are based upon a combination of number of furnaces and total throughput by weight. While we have focused largely on the total number of furnaces each location has, we have also taken into consideration total throughput. As an example “Dauch Corp.” in Mexico (formerly AAM) is ranked in the #5 position in terms of number of furnaces but based upon total throughput it might be the largest single location heat treater in North America.
• It comes as no surprise to us that a majority of the firms on this list are automotive related-no other industry in North America does as much heat treating as the auto industry.
• There can be no better indication of how the auto industry has embraced LPC (Low Pressure Carburizing) for transmission components that a look at this list-7 out of the 15 locations on this list are largely LPC based.
• While we are on the topic of LPC, we will mention that while CFC fixturing has gained a foothold in the Vacuum Carburizing industry, a majority of the facilities on this list doing LPC are still using cast fixturing.
• Our list is dominated by “atmosphere” heat treating as opposed to vacuum, with “Tinker Air Force Base” being the only “all vacuum” facility on our list. We are well aware that there are some large aerospace vacuum locations in North America (Pratt & Whitney in Maine with 10 vacuum furnaces comes to mind) however at the end of the day none come close to the names on our list in terms of throughput or number of furnaces.
• 9 of the names on this list are located in the USA, 4 in Mexico and 1 in Canada.
• While we do not for a second claim this list is 100% accurate, we do boldly state that we are not aware of any other lists more accurate than this one.
• As always we appreciate the input we received from each company on this list and we look forward to your thoughts and comments.

1) Ford Motor Company Sharonville, Ohio Transmission Facility, (64) ECM LPC Cells. We are quite comfortable in suggesting that the Ford Sharonville, Ohio Transmission facility is the single largest captive heat treat facility in North America. Ford was one of the first automotive companies to embrace vacuum carburizing and the end result is that this plant now has 64 ECM LPC cells with 20 bar nitrogen gas quench systems. 

It is worth noting that this facility has almost 2.5 million cubic feet under roof with almost 2,000 employees; “The Ford Motor Company Sharonville Transmission plant is a transmission manufacturing facility located in Sharonville, Ohio, United States. Established in 1958, Sharonville has long been the backup site for overflowing work at the Ford Motor Company Livonia Transmission plant. It is also where the Ford Crown Victoria’s transmission was once assembled for over three decades. With the Crown Victoria now discontinued, the Sharonville transmission plant currently overseas production of the 64140 6-speed automatic transmission – also known as the Torqshift – destined for the Ford Super Duty line of heavy-duty trucks. Sharonville is where the Ford/GM 10R80 10-speed transmission is assembled. The facility also manufacturers individual gears for the 6R80, 6R140, 6F35, 6F50/55, 8F57 transmissions. These gears are then shipped to other Ford manufacturing plants like the Ford Motor Company Van Dyke Transmission plant and the Ford Motor Company Livonia Transmission plant

2) JATCO Aguas Caliente, Mexico, (60) ECM LPC Cells. A brand-new entry on our list is JATCO” (Japan Automatic Transmission Co., Ltd.) in Aguas Caliente in Mexico. The firm supplies continuously variable transmissions and maintains a very large vacuum carburizing (LPC) department which consists of 60 carburizing cells with hot and cold oil quenching along with gas quenching. 

3) GKN Driveline, Newton, North Carolina, (39) ECM LPC Cells. In our third position we find another automotive parts supplier, GKN in Newton, NC. While not one of the first to invest in vacuum carburizing systems they certainly jumped on the bandwagon after vacuum carburizing proved it’s value. The company now has 39 LPC cells provided by ECM with 20 bar nitrogen quenching.

4) Allison Transmission, Speedway, Indiana, (38) Atmosphere Furnaces (various suppliers).  In our fourth position we find the Allison Transmission Campus in Speedway, Indiana. This facility is the world’s largest manufacturer of fully automatic transmissions for medium- and heavy-duty commercial vehicles. Their very extensive in-house heat-treating department boasts the largest number of batch IQ furnaces in one location in North America, (25) 36”x 48” IQ Furnaces and (5) 30” x 48” IQ Furnaces. These furnaces are spread out over 4 locations on the same campus with a total of over 80,000 square feet. In total the heat treat department at Allison includes this equipment, sourced from a few different furnace builders including “Surface Combustion”. 

• (30) IQ Furnaces
• (36) Temper Furnaces
• (6) Pit Nitride Furnaces
• (2) Rotary Furnaces
• (12) Induction hardeners

5) “Dauch Corporation” (Formerly Axle & Manufacturing Holdings), Silao, Mexico (approximately 31 atmosphere furnaces).  In 2012 auto parts supplier American Axle & Manufacturing (AAM) formally opened a new plant in the city of Silao, Guanajuato, Mexico. Since that time this facility has grown to encompass roughly 10 different plants, 7 of which offer heat treatment. This posed an issue for “The Monty” in terms of ranking-does this qualify as a single location heat treat? At the end of the day, we decided that as this is one complex it will for our purposes be considered a single location. The amount of heat treating in this complex is staggering, 6 pusher furnaces (2 single row, 2 two row and 2 four row), almost 20 batch IQ units, 36″ X 48″ X 36″, several normalizing lines, two mesh belt carburizing lines and multiple tempering units, washers and endo generators. Furnace suppliers include AFC-Holcroft. For sheer throughput in terms of pounds per hour this must be one of the largest captive heat treats in North America-in terms of number of furnaces we are going to rank “Dauch Corp.”, in Silao as the fourth largest in North America. 

6) John Deere Waterloo, Iowa, Approximately (31) Atmosphere Furnaces. As one of the world’s largest manufacturers of agricultural machinery, heavy equipment, forestry machinery, diesel engines, drivetrains used in heavy equipment, and lawn care equipment we are sure the company needs no introduction. Their location in Waterloo, Iowa is substantial with a total of 31 furnaces which are a mixture of batch IQ’s, rotary hearth and continuous. The equipment comes from a variety of furnace suppliers including Ipsen, AFC-Holcroft & Surface Combustion. We have to add that this is a very clean, well organized facility which comes as no surprise. 

7) Allison Transmission (Formerly Dana Fairfield Manufacturing), Lafayette, Indiana, Roughly (26) Atmosphere Furnaces. The heat treat department of this facility covers over 65,000 square feet (6,000 square meters) and in it we find 9 pusher lines, 2 nitriding systems, 2 large annealers, several pit carburizing systems, multiple batch IQ lines and a very substantial induction hardening footprint. Incidentally while this is a very impressive heat treat facility it represents only a fraction of the over 700 heat treating systems which Dana operates around the globe.

8) Linamar, Guelph, Ontario, Canada (31) Atmosphere Furnaces In our eighth  position we find a Canadian company, auto parts supplier Linamar. Linamar is a global company with many locations around the world doing heat treating however their largest heat treat department is in Guelph, Ontario. Roughly 25 years ago the firm made the decision to bring heat treating in house while at the same time deciding that going forward they would concentrate on batch processing as opposed to continuous. This plant now has twenty five AFC-Holcroft 36” X 48” X 36” batch IQ furnaces in place combined with five KGO & ALD vacuum nitriders and a rotary hearth furnace.

9) General Motors Ramos Arizpe, Mexico (30) ECM LPC Cells. The heat treating department of this engine and transmission components plant consists of 2 ECM systems with gas quenching for a total of 30 cells. 

10) Tinker Air Force Base, Oklahoma. (27) vacuum furnaces. Tinker Air Force Base in Oklahoma is one of the largest US Air Force bases in the USA-to give you a perspective on the size with, 9,000 employees it is the largest single location employer in the state. This site at last count had 27 vacuum furnaces in various configurations which includes horizontal, bottom loading and oil quenching. Furnace suppliers include Ipsen. 

11) Stellantis, Kokomo, Indiana. (27) Furnaces, 20 ALD LPC w HPGQ, (7) gas Nitriders (Aichelin and Nitrex). In 1956 Chrysler invested in a transmission facility in Kokomo, Indiana, a facility which now covers 3.1 million square feet (please note that there are several facilities in Kokomo, our interest is in the transmission facility). For many years now this plant which originally was called Chrysler, and subsequently FCA Kokomo before being renamed Stellantis had what was probably the largest captive heat treat in North America. At one time it included 7-Three row Holcroft Pusher Furnaces, 6-Lindberg 36 X 72 X 36 Batch IQ furnaces, 3-Holcroft single row pushers, 2- Surface rotary furnaces, 2-Seco Rotary Furnaces, 4-ECM vacuum nitriding furnaces, 30-tempering furnaces and several ECM vacuum carburizing systems. While the heat treat department is smaller than it once was it is still one of the larger in house heat treat departments in North America with a total of (20) ALD LPC Cells and (7) gas nitriders. 

12) Dana Toluca, Mexico. (24) Batch IQ Furnaces.  The Dana facility in Toluca, Mexico is one of three Dana facilities in North America which makes our list. This plant produces transmission components and has one of the largest batch IQ installations in North America. This facility is approximately 16 years old and has a total of 24 Surface Combustion batch IQ furnaces, each with working dimensions of 36″ X 48″ X 36″-this makes them the third largest in North America in terms of number of IQ’s, behind Allison Transmission in Indianapolis and auto parts supplier Linamar. All of the furnaces rely on an endothermic atmosphere with some of the furnaces incorporating press quenching. For a number of reasons Toluca has always gone the route of batch furnaces as opposed to continuous, most probably because of tighter control and more flexibility. 

13) Detroit Diesel, Redford Michigan, (24) ECM LPC Cells. Detroit Diesel, a major American engine manufacturer, is headquartered in Redford Township, Michigan where it operates its massive 3-million-square-foot flagship manufacturing plant. The plant produces approximately 400 engines, 250 transmissions, and 1,300 axles every single day. Their heat treatment department consists of 24 ECM LPC cells with gas quenching for heat treating large truck axle rings and pinions.

14) ZF Transmission, Grey Court, South Carolina. (16) ALD Carburizing Cells and (2) Ipsen Pusher lines. ZF is a German company which ranks amongst the largest suppliers of automotive transmission components in the world. The location in Grey Court, SC opened in 2012 and became a hub for ZF’s work in large-scale transmission production, including eight- and nine-speed automatic transmissions. ZF is another company which made the decision to go with vacuum carburizing and the end result is that this facility has two ALD “Modultherm” systems in place with a total of 16 carburizing cells and 2 Pusher lines for annealing supplied by Ipsen.

15) Dana Corp., Queretaro, Mexico, (Approximately (17) Atmosphere Furnaces). Number 15 on our list is yet another large auto parts maker, Dana Corporation, Queretaro, Mexico. While Dana has numerous facilities around the globe that include heat treating the largest is an enormous complex in the Mexican city of Queretaro with several large, separate in-house heat-treating departments. There are 3 separate facilities here, Dana Forja which has a heat-treating department doing annealing in continuous furnaces, Dana Cardanes which has 7 batch IQ furnaces, roughly 40 induction lines and 11 tempers and Dana, ENCO which has 2 AFC-Holcroft UBQ furnaces along with 4 pusher furnaces (as of 2020).