DEXRON is the trade name for a group of technical specifications for automatic transmission fluid (ATF) created by General Motors (GM). The name was first registered as a trademark and later evolved into a brand of GM. GM licenses the name and specifications to companies that manufacture the fluid and sell it under their own brand names. Not all DEXRON fluids are licensed by GM for reselling under another brand name. To be licensed, the product must have a license number that begins with the letters B through J and include a "DEXRON Approved" sticker on its container. Like many automobile manufacturers, GM uses transmissions sourced from other suppliers or transmission manufacturers around the world; many of these may use their own unique fluid.
Originally, the DEXRON name was only associated with automatic transmission fluids, though GM later released DEXRON gear oils and other lubricants under the DEXRON brand.GM Expands Family of DEXRON® Branded Oils, Lube on News GM.com, 11 Jan 2013
GM Automatic Transmission Fluids (ATF) The original DEXRON (B) transmission fluid was introduced on April 1, 1967. Over the years, the original DEXRON (B) was supplanted by DEXRON-II (C), DEXRON-II (D), DEXRON-II (E), DEXRON-III (F), DEXRON-III (G), DEXRON-III (H), DEXRON-VI (J), DEXRON HP, DEXRON LV ATF HP, and DEXRON ULV, which is the latest fluid to date. GM has upgraded the DEXRON's specifications over time. The newer fluids are not always backward-compatible with previous fluids. Newer 6, 8, 9, and 10-speed transmissions, as well as plug-in hybrid (PHEV) and electric vehicle (EV) transmission technologies, require specialized fluids to operate properly. There remains a market for older fluids that claim to meet the earlier fluid specifications. See the details below for the backward compatibility of each fluid.
Before DEXRON: 1937–1967 1937 – Motor Oil
The automatic safety transmission was first offered as an extra-cost option by the Oldsmobile Division of GM in the fall of 1937 for their Six and Eight models. It was only used during the 1938 and 1939 model years. The automatic safety transmission used the same seasonal grade of motor oil as the engine for lubrication and hydraulic functions.
The Automatic Safety Transmission was a four-speed transmission that could shift powerfully without needing a regular clutch. The transmission was called the Automatic Safety Transmission (AST) because the clutch operation was reduced to one-third of that required by a conventional transmission. The clutch was only necessary when starting or stopping the car.
The AST had two driving ranges (low and high). In low range, the transmission would shift from 1st to 2nd gear and then hold in 2nd. In high range, the transmission would start in 1st gear, jump to 3rd, then shift to 4th gear. The driver could change ranges with a flick of a finger.
1939 – Hydra-Matic Drive Fluid Released in 1939, the 1940–1949 GM Hydra-Matic Drive was used by the Oldsmobile, Cadillac, and Pontiac divisions. 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 SAE 20 engine oil. This fluid was composed of a Group 1 base oil and additives to reduce oxidation, foaming, rust, corrosion, varnish, and sludge buildup. This was the world's first automatic transmission fluid, designed for the world's first mass-produced automatic transmission.The World's First Mass-Produced Automatic Transmission
This fluid had cold-weather performance problems, which led to the need for an improved fluid, the Type "A" fluid, in 1949. The Hydra-Matic drive fluid was only available at GM dealerships. As a result, regular SAE 20 engine oil was being used in its place at filling stations and repair garages. Engine oil was only approved as a temporary fill fluid and led to transmission problems.
1949 – Type "A" Fluid
In 1949, General Motors (GM) established an Automatic Transmission Fluid (ATF) Committee (GM ATF Committee). The GM ATF committee established fluid specifications and a qualification procedure to eliminate unsatisfactory fluids and, at the same time, provide the car owner with a means of identifying qualified fluids. The GM ATF Committee released a new Type "A" fluid specification.The Present Status of Automatic Transmission Fluid, Type AIs The Torque Converter Going To Be “It”? GM partnered with the Armour Research Foundation for fluid and qualification testing. Fluids that met the GM qualification requirements were issued an Armour Qualification (AQ) license number of AQ-ATF-xxx. Example (AQ-ATF-101). The license number had to be displayed on the fluid container.AUTOMATIC TRANSMISSION FLUID, TYPE-A, FOR PASSENGER CARS
As a result, qualified GM automatic transmission fluid was made available at retailers and service garages in many places.
From 1949 to 1951, there were only two licensed fluids:
GM Type "A" Automatic Transmission Fluid License No. AQ-ATF-101 Texaco Texamatic Fluid Type "A" License No. AQ-ATF-102
This was the first GM automatic transmission fluid that was made available for sale at retailers other than GM dealerships. In 1951, GM began licensing more Type "A" fluids, which led to several hundred brands of licensed Type "A" fluid on the market. This fluid is backward compatible with the Hydra-Matic Drive fluid produced from 1940 to 1949.
It is important to understand that every automatic transmission produced by any vehicle manufacturer (Oldsmobile, Cadillac, Buick, Chevrolet, Pontiac, GMC, Ford, Mercury, Lincoln, Chrysler, Dodge, Desoto, Packard, and Studebaker) used motor oil or the GM Type "A" transmission fluids from 1949 to 1958.
In 1950, Ford released their 1951 Fordomatic 3-speed transmission, which used the GM Type "A" fluid. In 1952, Chrysler released their 1953 Powerflite 2-speed transmission, which also used GM Type "A" fluid.
This fluid was first used in the following transmissions:
1948 Buick Dynaflow 2-Speed Semi-Automatic Transmission 1950 Chevrolet Cast Iron Powerglide 2-Speed Semi-Automatic Transmission 1953 GM Dual Range Hydra-Matic 4-Speed Automatic Transmission 1953 Chevrolet Powerglide 2-Speed Automatic Transmission 1953 Buick Dynaflow 2-Speed Automatic Transmission 1956 Buick Dynaflow 2-Speed Automatic Transmission 1956 GM Controlled Coupling Hydra-Matic 4-Speed Automatic Transmission 1957 Chevrolet Turboglide 3-Ratio Automatic Transmission 1957 Buick Flightpitch Dynaflow 3-Ratio Automatic Transmission
1957 – Type "A" Suffix "A" Fluid
In 1957, GM released a new Type "A" Suffix "A" fluid specification.DEVELOPING TRANSAXLE FLUID This fluid was better suited for the higher fluid temperatures caused by the unique torque convertersPolyphase Torque ConverterThe Buick Flight Pitch DynaflowCHEVROLET AUTOMATIC TRANSMISSION and higher power engines of the day. The fluid specification was revised again in 1958, 1959, and 1960.Automatic Transmission Fluid Viscosity at Low Temperature and its effect on transmission performance
GM continued the licensing program, allowing oil companies to produce the new Type "A" suffix "A" fluid under their own brand name. GM-licensed fluids had the armor qualification license number of AQ-ATF-xxxA. Example (AQ-ATF-752A) stamped on the can This fluid is backward compatible with the Type "A" and Hydra-Matic Drive fluids produced from 1940 to 1957.
In 1959, Ford released its own automatic transmission fluid specification (M2C33-A) and stopped using GM fluid specifications. Also in 1959, Toyota released their Toyoglide 2-speed transmission, which used the GM Type "A" suffix "A" fluid.
This fluid was first used in the following transmissions:
1961 GM Roto-Hydra-Matic 3-Speed Automatic Transmission 1961 Buick Dual Path 2-Speed Automatic Transmission 1961 Mercedes-Benz K4A 025 4-Speed Automatic Transmission 1962 Chevrolet Aluminum Powerglide 2-Speed Automatic Transmission 1964 GM Hydra-Matic 400 3-Speed Automatic Transmission 1966 GM Hydra-Matic 425 3-Speed Automatic Transmission
DEXRON fluids 1967 – DEXRON (B)
DEXRON (B) was released on April 1, 1967. The original fluid better retained the initial properties of the previous Type "A" Suffix "A" fluid (Several thousand cycles compared to 1000 cycles).https://www.sae.org/publications/technical-papers/content/680038/ Dexron Automatic Transmission Fluid DEXRON (B) was composed of a more stable, less reactive, hydrotreated Group 1 base oil plus additives to help prevent foaming, oxidation, and damage from elevated temperatures.https://www.sae.org/publications/technical-papers/content/710838/ Automatic Transmission Fluid Viscosity Requirements This was the first GM ATF to advertise 24,000 miles between changes.
This was the first GM ATF to require red dye as an aid in fluid leak detection. Prior to this fluid, GM ATF was the same color as engine oil. Aftermarket ATF was available with red dye.
GM DEXRON (B)-licensed products have a license number on the container that begins with the letter B. Example: B10001. This fluid is backward compatible with all Type "A" suffixes and the Type "A" fluids produced from 1949 to 1966.
This fluid was first used in the following transmissions:
1969 GM Hydra-Matic 180 3-Speed Automatic Transmission
1973 – DEXRON-II(C) The original DEXRON (B) fluid, as well as earlier GM transmission fluids, used sperm whale oil as an additive to coat internal transmission parts to prevent corrosion and rust. The U.S. Endangered Species Act banned the import of sperm whale oil, so the DEXRON (B) fluid additive package had to be reformulated. In 1973, GM introduced DEXRON-II(C) (GM Spec GM6032M).Dexron-II Automatic Transmission Fluid PerformanceTransmission Air Breathing Suppressor (TABS) Valve - A Device for Improving Automatic Transmission Fluid Life
DEXRON-II(C) was composed of a more stable, less reactive, hydrocracked Group 2 base oil plus a revised additive package with corrosion and rust inhibitors such as jojoba oil; however, the additive package caused problems with corrosion-prone solder in a relatively small number of GM's transmission fluid coolers. After discovering the corrosion problem, GM updated the fluid specification again and released DEXRON-II(D) in 1975.The New York Times April 17, 1975: Transmission Problems in Cars Linked to Ban on Whale Killing
GM DEXRON-II(C) licensed products have a license number on the container that begins with the letter C. This was the first GM ATF to advertise 50,000 miles between changes. This fluid is backward compatible with all previous DEXRON fluids as well as the Type "A" Suffix "A", and the Type "A" fluids produced from 1949 to 1966.
1975 – DEXRON-II(D) In 1975, GM released the DEXRON-II(D) specification (GM6032M). DEXRON-II(D) was composed of Group 2 base oil plus an additive package with alternative corrosion and rust inhibitors. The revised corrosion and rust inhibitors made the new fluid hygroscopic, which, while it was not a major problem in automatic transmissions, made DEXRON-II(D) unsuitable for other hydraulic systems in which it was commonly used. GM DEXRON-II(D) licensed products have a license number on the container that begins with the letter D. This fluid is backward compatible with all previous DEXRON fluids as well as the Type "A" Suffix "A", and the Type "A" fluids produced from 1949 to 1966.
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: A 4th gear (overdrive) A Torque Converter Clutch (TCC) Front Wheel Drive (FWD)