A look at changes in automatic transmission fluid

Sept. 26, 2018
Transmissions have evolved into high-tech engineering marvels — and so has the fluid that they depend on to operate as intended by the OEMs.

Earlier this year Ford donated a brand new 10R80 10-speed automatic transmission from a 2017 Ford F-150 to our school for training purposes. I was very excited because this is one of the newest transmission technologies available. As I positioned it on my workbench I looked across the shop at another transmission with incredible technology, the 1940 General Motors Hydra-Matic 4-speed, the world’s first mass-produced automatic transmission.

Both of these amazing transmissions as well as the hundreds of others that have come along in the past 78 years were designed to use an Automatic Transmission Fluid (ATF) that had been customized for that very transmission. Without the specified ATF, these transmissions cannot perform as designed. This article will focus on the evolution of ATF and the reasons why using the right fluid can make a big difference. I know that some of you do not believe that the factory specified fluid is the best choice for your transmission, but if you will continue reading, you may change your mind by the end of this article.

Figure 1 - 2017 Ford F-150 10R80 10-Speed Automatic Transmission

Warning – Historical content!

To understand the evolution of ATF, it is helpful to have a basic understanding of the development of the automatic transmission. Prior to 1940, manually shifted transmissions were the only option for the majority of automobiles and trucks available. Prior to 1928, none of those transmissions contained synchronizers. This means that every shift could take up to 10 seconds to complete because the driver had to use a difficult process called Double Clutching to avoid gear clash.

A young engineer named Earl A. Thompson designed and patented the first synchronized manual transmission in 1922.  Cadillac purchased Thompson’s patents and with Thompson’s help offered refined version of it as the Synchro-Mesh Transmission in 1928 Cadillacs. This invention was only the first step towards Thompson’s goal of designing a fully automated transmission.

1938-1939: Strange beginnings —motor oil

By 1934 Thompson’s group had developed a 4-speed transmission called the Automatic Safety Transmission (AST). It was given that name because clutch operation was reduced to one third of that required by a conventional transmission. The AST used the same seasonal grade of motor oil as the engine for lubrication and hydraulic functions.

In the 1930s, crude oil was refined into a Group I base oil by a process called solvent refining. Motor oil was created by combining chemical detergents (additives) with the base oil to prevent sludge and varnish buildup. 

1939-1941: Specialty transmission fluids are developed

For the 1939 model year, Chrysler offered the “Fluid Drive.” This car had a three-speed manual transmission connected to a conventional clutch. The clutch was connected to the engine through a sealed fluid coupling. Depressing the clutch pedal was not needed unless the driver desired a different transmission gear. The fluid coupling was partially filled (80 percent) with a special Mopar Fluid Drive Fluid. The transmission gearbox used regular S.A.E. 80-160 gear oil.

Figure 2 - 1939-1951 Mopar Fluid Drive Fluid

The world’s first mass-produced fully automatic transmission, the Hydra-Matic Drive, was released for 1940 model year Oldsmobiles. This was the first transmission that combined several new and existing technologies (planetary gears, bands, servos, governor, throttle valve, valve body, and fluid coupling) into one fully automatic package.

The Hydra-Matic Drive used a specialized lubricant called GM Transmission Fluid No. 1. By using the term "fluid" rather than "oil" they hoped to discourage the previously accepted practice of using S.A.E 20 engine oil. The only source of this new transmission fluid was at Oldsmobile dealerships. In 1941, Cadillac also used the Hydra-Matic Drive.

Figure 3 - Two examples of GM Hydra-Matic Fluid 1940-1949

Oldsmobile and Cadillac recommended the fluid be checked every 1,000 miles and changed every 5,000 miles. The Hydra-Matic drive was a huge success with over thirteen million transmissions being produced over the next 16 years.

The Hydra-Matic Drive fluid was created by combining several chemical additives with the Group I base oil. These additives helped to prevent oxidation, corrosion, foaming, sludge and varnish buildup, and clutch chatter. They also helped maintain viscosity, chemical stability, and oil cleanliness.

1942–1945: World War II – A need for reliable lubrication for severe conditions

On December 7, 1941 the Japanese bombed Pearl Harbor and drew the United States into World War II. As a result, the U.S. Military ordered all car manufacturers to stop production of automobiles and to start building war machinery.  During the war, each Army M-5 and M-24 Tank used two modified Hydra-Matic Drive transmissions powered by Cadillac V-8 engines. The relatively new Hydra-Matic Drive and its special fluid were now being used under very rough conditions. These conditions helped GM make improvements in the transmission.

1946-1948: Post-war experimentation and growing pains

After the war Buick, Chevrolet, and Chrysler were experimenting with different configurations of fluid drives and torque converters. They were interested in developing a less expensive and smoother shifting transmission than the Hydra-Matic. In 1948 Buick offered a new 2-speed transmission with a torque converter called the Dynaflow. The Dynaflow’s torque converter created so much heat that it impacted the life of the existing fluid. A better fluid was needed.

1949-1958: Mass marketed fluids

By 1949, it had become obvious that a single source (dealership only) transmission fluid supply system was a mistake as repair shops world-wide were substituting S.A.E 20 motor oil in place of the recommended transmission fluid. To be successful, the Hydra-Matic transmission fluid would need to be available at every service station and gas station.

In 1949, GM released the Type “A” fluid standard. This was an improved fluid with a longer service interval of 15,000 miles. GM used the Armour Research Foundation for “Armour Qualification” (AQ) fluid tests. Passing the qualification test would allow any independent oil company to produce, distribute, and sell GM approved Type A transmission fluid. 

Fluids that passed the AQ tests were assigned an (AQ-ATF-xxx) qualification number. This number had to be marked on the fluid can. By 1955, 482 AQ licenses were granted with 229 marketers nationwide (mostly service stations) and several in other countries. Almost every automatic transmission produced by any vehicle manufacturer used the GM Type-A transmission fluids from 1949-1958. Chrysler, Dodge and Desoto were an exception with their fluid drives.

Figure 4 - Five examples of Type A fluid 1949-1957

During the 1950s, GM released 5 new transmissions that used unique multi-element torque converters. These torque converters caused so much heat and fluid oxidation that the GM Type A fluid specification had to be revised in 1951 and again in 1957.

During the same time period, Ford released their first three new automatic transmissions. Chrysler released their first two automatic transmissions. These torque converters got very hot. Cooling fins and air ducting was added to cool them. There was a need for an improved transmission fluid that could withstand higher heat for longer periods of time.

In 1957, GM released the "Type A Suffix A" standard. Fluids that passed the new AQ tests were assigned a new (AQ-ATF-xxxA) qualification number.

Some fluid makers produced counterfeit qualification numbers like WLCO-ATF-334 Suffix A with the apparent intent of tricking people into purchasing their unapproved and less expensive fluids. The WARCO can in the photo is one early example. Counterfeit fluid makes up about 50 percent of the fluid market today in 2018.

Figure 5 - Seven examples of Type A Suffix A fluid 1957-1967

1959-1976: The Big 3 diverge

Up until this date, Group I base oils have typically had a viscosity index (VI) of 80-120. In the 1960s a new refining process called Hydro-treating improves Group I base oil quality giving it a VI closer to 120 (Higher is better). In 1971 an improved refining process called Hydrocracking produces a Group II base oil (A better quality base oil).

In 1959, Ford developed and released their own fluid standards: Types A and B. Type D was released in 1961, Type F in 1967, and Type-CJ in 1974. Ford also released several new 3-speed transmissions: The C-4 and C-6 in 1964, and the C-3 in 1974.

Figure 6 - In 1959 Ford started releasing their own fluid specifications

Chrysler continued using the Type A Suffix A fluid and released two new 3-speed transmissions: The A904 in 1960 and the A727 in 1962. In 1964, Chrysler released their own fluid standard MS-3256 followed by MS-4228 in 1966. Chrysler released two new 3-speed transmissions in 1968: The A998 and A999.

Figure 7 - In 1996 Chrysler started releasing their own fluid specifications

GM revised the Type A Suffix A fluid specification two more times in 1959 and 1960. GM also releases six new transmissions including the 2-speed aluminum Powerglide in 1962 and the 3-speed TH400 in 1964. (The Powerglide is very hard on transmission fluids because of high torque converter fluid temperatures and oxidation).

In 1967, GM released the new Dexron (B) fluid specification This improved fluid had a longer service interval of 25,000 miles. GM also releases three more 3-speed transmissions.  This is followed by the Dexron-II (C) Fluid Specification in 1973.

Figure 8 - Eight generations of the Dexron fluid 1967-2017

1977-1990: Fuel economy, overdrive and the Torque Converter Clutch

As a result of the 1973 OPEC Oil Embargo and fuel shortages, the U.S. government created the Corporate Average Fuel Economy (CAFE) regulations in 1975. The regulations were to be fully implemented by the 1978 model year. The automotive industry responded by changing to three typically unused transmission technologies: 1. A 4th gear (overdrive) 2. A Torque Converter Clutch (TCC), and 3. Front Wheel Drive (FWD).

The introduction of the TCC led to customer complaints of a shudder while driving. All vehicle manufacturers made changes to their ATF specifications and the controls of their TCC to try and alleviate the problem. Chrysler released the ATF +2 fluid specification in 1980. Ford released the M2166-H fluid specification in 1981 and the Mercon fluid Specification in 1987.

Toyota, who had been producing automatic transmissions since the 2-Speed Toyoglide in 1963, continued using various GM ATF specifications until 1988. The Type T Fluid Specification was released in 1988, followed by Type T-II in 1993, Type T-IV in 1996, and the WS fluid in 2002.

Figure 9 - In 1993 Toyota started releasing their own fluid specifications

In 1989 The first Group IV Base oil fully synthetic polyalphaolefins (PAO) ATF was released by Mobil.

1991-1995: Electronic controls and improved fluids

In the 1990s, Electronic controls of the transmission phased out the old hydraulic/mechanically controlled system. Chrysler and Toyota were first to market with electronic controlled transmission systems in 1988, Ford followed in 1989, and GM in 1991.

Electronic control of shift pattern (when does it shift), shift timing (how long it takes to shift), shift quality (shift feel), line pressure, and TCC apply and release rates were all affected by cold temperature performance of the ATF flowing through solenoids GM Revised their Dexron fluid specification two times: Dexron-II (D) and Dexron-II (E) in 1992 with improved cold temperature performance.

In 1993, Chevron patented a process called ISODEWAXING produces Group III base oils. Group III base oils have a Viscosity Index (VI) of 120-141 (Very close to that of Group IV synthetic base oils).

In 1995, GM released the new Dexron-III (F) fluid specification This was an improved fluid with better compatibility with newer clutch friction materials, seals, etc. and it had better oxidation stability which gave it a longer service interval of 50,000 miles.

1996-2007: Variable Capacity Converter Clutch

In 1994-1995, some early OBD-II phase-in vehicles experienced a P0300 DTC (Random Misfire). Engineers determined that road forces being transferred through the TCC were affecting the normal rotational fluctuations of the crankshaft and tricked the ECM into thinking there was a cylinder misfire.

The solution was to create a new kind of TCC that would normally slip around 35 rpm. GM called it the Variable Capacity Converter Clutch (VCCC), other manufacturers had their own names. Some VCCC systems had a shudder or vibration during normal operation. Engineers tried several computer calibration changes, but a revised fluid was also needed to address the issue.

Ford released the new Mercon V Fluid Specification in 1996, GM released the Dexron-III (G) Fluid Specification in 1998, and Chrysler released the MS-9602 Change C Fluid Specification in 1999.

In 1999 Ford and DaimlerChrysler offered a 5-speed automatic transmission, GM followed in 2000. In 2001, DaimlerChrysler revised their fluid specifications to ATF +3 and then ATF +4 in 2003. GM revised their Dexron-III H fluid specification in 2003.

2008-2016: Low viscosity fluids

In a joint venture, Ford and GM collaborated on the development of a new 6-speed FWD transaxle (6T70/6F50) and an RWD transmission (6L80/6R140). Both companies would share the designs and build their own transmissions. The design of these transmissions required a new fluid.

In 2005, Ford released the Mercon Low Viscosity (LV) fluid and GM released the Dexron VI specification. Both of these fluids were comprised of PAO Group IV base oils or blends. This resulted in a fluid change interval of 100,000 miles.

Toyota and DaimlerChrysler also offered 6-speed transaxles but kept their existing fluid specifications. These 6-speed transmissions were built to help meet the upcoming 2008 Tier-2 Emissions Regulations.

Important Note: In 2011, GM inactivated the Dexron III (H) fluid specification. 2016, GM releases the Dexron-III (K) Fluid Specification for manual transmissions and power steering systems only. All ATF additives were removed, do not use it as ATF!

With increasing CAFE regulations, smaller engines with very narrow torque bands were being put in cars with low volume oil capacity 6, 7, 8, and 9-speed transmissions. Lexus, GM, and ZF all offer 8-speed transmissions, ZF offers a 9-speed FWD transaxle. Another fluid change is needed.

In July of 2013, GM released the Dexron-HP (LV) Fluid Specification. In 2014, Ford released the Mercon Ultra Low Viscosity (ULV) Fluid Specification. The GM Dexron-VI Fluid Specification is revised again. ZF releases their LIFEGUARDFLUID 8 fluid specification.

Oil Refining

In 2015 a Group III+ (a Gas-to-Liquid (GTL) base oil) is released that has a viscosity index of 144, same as that of some Group IV base oils. In 2017, GM revises the Dexron-HP (LV) Fluid Specification to include Group III+ base oil.

2017-2019: Ultra low viscosity fluids

By January 2017, full compliance with Tier-3 Emissions Regulations was required. As you may know, Ford and GM collaborated again on the development of a new 10-speed rear wheel drive transmission (10R80/10L90) and a 9-speed front wheel drive transaxle (9T50). The ULV fluids developed in 2014 the required for the 10-speed models.

Conclusion

As you have read, almost every change in transmission technology over the past 78 years required a specialized fluid to go with it. Counterfeit fluids, misleading labels, and low prices are all very confusing to the general public.  There is not room enough in this article to cover all of the specification details for each fluid. I have done the research and I will only use the factory fluids in my own vehicles. I encourage you to do the same. Best wishes!

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