Automatic Transmission Fluid
Encyclopedia
Automatic transmission fluid (ATF) is the fluid used in vehicles with self shifting or automatic transmissions. It is typically colored red or green to distinguish it from motor oil
and other fluids in the vehicle. On most vehicles its level is checked with a dipstick
while the engine is running.
The fluid is a highly specialized oil optimized for the special requirements of a transmission, such as valve operation, brake band friction and the torque converter as well as gear lubrication.
ATF is also used as a hydraulic fluid in some power assisted steering systems, as a lubricant in some 4WD transfer case
s, and in the manual transmission
s of many modern front-wheel drive
cars.
There are many specifications for ATF, such as the DEXRON
and MERCON series, and the vehicle manufacturer will identify the ATF specification appropriate for each vehicle. The vehicle's owner's manual will typically list the ATF specification(s) that are recommended by the manufacturer.
Automatic transmission fluids have many performance-enhancing chemicals added to the fluid to meet the demands of each transmission. Some ATF specifications are open to competing brands, such as the common DEXRON
specification, where different manufacturers use different chemicals to meet the same performance specification. These products are sold under license from the OEM responsible for establishing the specification. Some vehicle manufacturers will require "genuine" or Original Equipment Manufacturer (OEM
) ATF. Most ATF formulations are open 3rd party licensing, and certification by the automobile manufacturer.
Current OEM formulations are made from synthetic base stocks. Each manufacturer has specific ATF requirements. Incorrect transmission fluid may result in transmission malfunction or severe damage.
Synthetic ATF is available on aftermarket brands, offering better performance and service life for certain applications (such as frequent trailer towing).
The use of a lint free white rag to wipe the dipstick on automatic transmissions is advised so that the color of the fluid can be checked. Dark brown or black ATF can be an indicator of a transmission problem, vehicle abuse, or fluid that has far exceeded its useful life. Overused ATF often has reduced lubrication properties and abrasive friction materials (from clutches and brake bands) suspended in it; failure to replace such fluid will accelerate transmission wear and could eventually ruin an otherwise healthy transmission. However color alone is not a completely reliable indication of the service life of an ATF as most ATF products will darken with use. The manufacturer's recommended service interval is a more reliable measure of ATF life. In the absence of service or repair records, fluid color is a common means of gauging ATF service life.
as a friction modifier
. But since whale oil would break down at higher temperatures, cars produced in the 1970s and later would not be able to use whale oil because of the higher engine coolant temperatures employed to reduce emissions and save fuel. A moratorium on whale oil at that time prevented the continued production of older ATFs such as the original DEXRON formulation (Type B), and the Type A which preceded it. General Motors began marketing Dexron II Type C and later Dexron II Type D to replace the whale oil-derived fluids.
Motor oil
Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.Motor oils are derived from...
and other fluids in the vehicle. On most vehicles its level is checked with a dipstick
Dipstick
A dipstick is one of several measurement devices.Some dipsticks are dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid....
while the engine is running.
The fluid is a highly specialized oil optimized for the special requirements of a transmission, such as valve operation, brake band friction and the torque converter as well as gear lubrication.
ATF is also used as a hydraulic fluid in some power assisted steering systems, as a lubricant in some 4WD transfer case
Transfer case
A transfer case is a part of a four-wheel-drive system found in four-wheel-drive and all-wheel-drive vehicles. The transfer case is connected to the transmission and also to the front and rear axles by means of drive shafts...
s, and in the manual transmission
Manual transmission
A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...
s of many modern front-wheel drive
Front-wheel drive
Front-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...
cars.
Modern use
Modern ATF typically contains a wide variety of chemical compounds intended to provide the required properties of a particular ATF specification. Most ATFs contain some combination of rust preventatives, anti-foam additives, detergents, dispersants, anti-wear additives, anti-oxidation compounds, surfactants, cold-flow improvers, high-temperature thickeners, gasket conditioners, and petroleum dye.There are many specifications for ATF, such as the DEXRON
Dexron
Dexron is the trade name for a group of technical specifications of automatic transmission fluid created by General Motors . The name is a registered trademark of GM, which licenses the name and specifications to external companies which manufacture the fluid and sell it under their own brands...
and MERCON series, and the vehicle manufacturer will identify the ATF specification appropriate for each vehicle. The vehicle's owner's manual will typically list the ATF specification(s) that are recommended by the manufacturer.
Automatic transmission fluids have many performance-enhancing chemicals added to the fluid to meet the demands of each transmission. Some ATF specifications are open to competing brands, such as the common DEXRON
Dexron
Dexron is the trade name for a group of technical specifications of automatic transmission fluid created by General Motors . The name is a registered trademark of GM, which licenses the name and specifications to external companies which manufacture the fluid and sell it under their own brands...
specification, where different manufacturers use different chemicals to meet the same performance specification. These products are sold under license from the OEM responsible for establishing the specification. Some vehicle manufacturers will require "genuine" or Original Equipment Manufacturer (OEM
OEM
OEM means the original manufacturer of a component for a product, which may be resold by another company.OEM may also refer to:-Computing:* OEM font, or OEM-US, the original character set of the IBM PC, circa 1981...
) ATF. Most ATF formulations are open 3rd party licensing, and certification by the automobile manufacturer.
Current OEM formulations are made from synthetic base stocks. Each manufacturer has specific ATF requirements. Incorrect transmission fluid may result in transmission malfunction or severe damage.
Current fluids
- ATF+4 - Most Dodge, Jeep, and Chrysler
- Mercon V - Most Ford, Mercury, Lincoln
- Mercon LV - Some Ford(DuratecHE),MAZDA in Europe or Asia
- DexronDexronDexron is the trade name for a group of technical specifications of automatic transmission fluid created by General Motors . The name is a registered trademark of GM, which licenses the name and specifications to external companies which manufacture the fluid and sell it under their own brands...
VI - Most GM products, some Ford applications - ATF DW-1 - All Honda and Acura (except CVT)
- SP-III - All Hyundai, Mitsubishi and Kia (except CVT and dual clutch)
Synthetic ATF is available on aftermarket brands, offering better performance and service life for certain applications (such as frequent trailer towing).
The use of a lint free white rag to wipe the dipstick on automatic transmissions is advised so that the color of the fluid can be checked. Dark brown or black ATF can be an indicator of a transmission problem, vehicle abuse, or fluid that has far exceeded its useful life. Overused ATF often has reduced lubrication properties and abrasive friction materials (from clutches and brake bands) suspended in it; failure to replace such fluid will accelerate transmission wear and could eventually ruin an otherwise healthy transmission. However color alone is not a completely reliable indication of the service life of an ATF as most ATF products will darken with use. The manufacturer's recommended service interval is a more reliable measure of ATF life. In the absence of service or repair records, fluid color is a common means of gauging ATF service life.
History
In the 1950s, 1960s, and 1970s, ATF contained whale oilWhale oil
Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...
as a friction modifier
Friction modifier
Friction modifiers are added to lubricants to reduce the surface friction of the lubricated parts. Typically these are polar chemical compounds having high affinity for metal surfaces and possessing long alkyl chains....
. But since whale oil would break down at higher temperatures, cars produced in the 1970s and later would not be able to use whale oil because of the higher engine coolant temperatures employed to reduce emissions and save fuel. A moratorium on whale oil at that time prevented the continued production of older ATFs such as the original DEXRON formulation (Type B), and the Type A which preceded it. General Motors began marketing Dexron II Type C and later Dexron II Type D to replace the whale oil-derived fluids.