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How to Choose the Correct Automatic Transmission Fluid

by Larry Carley copyright

Automatic Transmission Fluid (ATF) is the lifeblood of your vehicle's transmission. The type of ATF your car, truck or SUV requires depends on the year, make and model of your vehicle, and the type of transmission. Different applications require different ATF fluids with specific additives and viscosity ratings. Every auto maker has their own unique performance requirements for the automatic transmission fluids they require. Note that we said "require" not "recommend." Those requirements are very specific and are essential to provide the correct lubrication and function inside your transmission. Use the wrong fluid in your transmission and you could be in for expensive trouble!

If the transmission fluid in your vehicle is low, or it is time to change the fluid, it is very important that you choose the correct type of fluid for your transmission. You can find that information in your owners manual. The ATF fluid type may also be printed on the ATF fluid level dipstick (if your transmission has a dipstick. Some do not.).

Most auto parts stores have application guides that can also help you choose the correct AFT for your transmission.

Transmission Fluid Level Checks

How to Check the Fluid Level in Your Transmission: The first thing to do is to find the transmission dipstick. It may have a RED handle (or another color or no color), and will located in a metal tube that is connected to the transmission. Do not confuse the transmission dipstick with the engine oil dipstick, which will be on the engine itself and may be color coded YELLOW.

For an automatic transmission to function normally, the fluid level must be between the "full" and "add" marks on the dipstick. If the fluid level is low, the transmission may slip or engage slowly. If the level is too high, the fluid can become mixed with air (aerated) causing shifting problems, slippage and noise.

dipstick fluid level
The dipstick will tell you if the ATF fluid level is Full or Low.

IMPORTANT: Check the level when the transmission fluid is WARM or HOT (not COLD). On most vehicles the level is checked while the engine is idling with the transmission in Park. Moving the gear selector thorough each gear position prior to checking the level will help assure an accurate reading.

Under normal driving conditions, a transmission should not use any fluid. A low level, therefore, usually indicates a leak. A visual inspection of the pan gasket and driveshaft seals will tell you where the fluid is going.

If the fluid level is low SLOWLY add about half a pint (half a liter) of ATF using a clean funnel. Then recheck the level. Continue adding small amounts of fluid as needed until the dipstick indicates FULL with the fluid warm or hot, the engine idling and the transmission in Park. DO NOT OVERFILL THE TRANSMISSION!

How to Check the Fluid Level in a Transaxle or Transmission that Lacks a Dipstick

NOTE: Many front-wheel drive cars with CVT (continuously variable) transaxles do not have a dipstick or filler tube for checking the fluid level. The auto makers who eliminated the dipsticks on these applications say they did so to prevent motorists from adding the wrong ATF to the transaxle (which would cause the CVT transaxle to fail!). CVT transaxles require a very specific type of fluid (see below).

Auto makers such as Audi, BMW, GM, Ford, Chrysler, Lexus, Mazda, Nissan, Honda, Toyota and Volkswagen who have sealed their transmissions also say the fluid never needs to be changed and should last upwards of 150,000 miles. Well maybe. Under "normal" driving conditions (no lead foot driving, heavy towing, hot desert driving or prolonged mountain driving), the fluid might last that long. But what if you are not a "normal" driver or your transmission starts to leak? Then you have to check the fluid level and add fluid as needed.

So how are you supposed to check the fluid level in a sealed transmission with no dipstick? The transaxle or transmission will have a filler plug somewhere on the side of the gear housing, similar to the filler plug on a rear axle differential. The plug may have a SQUARE head or inverted hex drive rather than a standard 6-point bolt head. Your owners manual may tell you where to locate this plug.

To check the fluid level in the transaxle or transmission, remove the filler plug. The fluid level inside should usually be at or just a bit below the opening of the filler plug. If the level is low, you will have to use a hose and a funnel to slowly add the correct fluid until the level is raised to where it should be. Or, you can fill a clean plastic squeeze bottle and add fluid by squirting it into the filler hole.

Here are some applications that do not have a dipstick:

5L40/5L50E 2004-05 CADILLAC CATERA
42RLE 2005-UP CHRYSLER 300 3.5L 2WD
NAG-1 2005-UP CHRYSLER 300 3.5L AWD
2007 & up Nissan Altima
AF23 2004-05 SATURN ION
4/5-Speed 2004-05 SATURN VUE

Check the Condition of the Automatic Transmission Fluid

Note how the fluid smells when you check the level on the dipstick. If it smells like burned toast and/or has a discolored brown appearance, the fluid is oxidized and needs to be changed.

You can also use a "blotter test' to determine the condition of the fluid. Put a few drops of ATF on a clean paper towel. Wait 30 seconds, then examine the spot. If the fluid has spread out and is pink, red or even light brown in color, the fluid is in satisfactory condition. But if the spot hasn't spread out and is dark brown in color, the ATF is oxidized and should be changed.

If the fluid has a milky brown appearance, it indicates coolant contamination. There is probably a leak in the ATF oil cooler inside the radiator that is allowing coolant to mix with the ATF. This is bad news and needs to be repaired immediately.

If the fluid is full of bubbles or is foamy, the transmission is probably overfilled with ATF. Other causes include using the wrong type of ATF or a plugged transmission vent.

Why ATF Breaks Down Over Time

Compared to motor oil, ATF has live pretty easy. There's no soot, gasoline or condensation from combustion blowby to contaminate the fluid. The only physical contaminants the fluid must deal with are particles that wear off the friction plates, gears and bearings inside the transmission. Most transmissions have some type of internal filter to keep the fluid clean. Some do a pretty good job, but others don't. Most Asian transmissions only have a plastic or metal strainer that can only trap the larger pieces of debris. The rest circulates with the fluid and accelerates wear. Changing the fluid is the only way to get rid of these contaminants.

Heat is the main concern for ATF. Automatic transmissions create a lot of friction, and friction produces heat. The fluid is constantly churning inside the torque converter and being pumped through metering orifices and hydraulic circuits. Every time the transmission shifts gears, the clutch packs generate even more heat that must be carried away by the fluid. The greater the load on the transmission, the more heat it generates and the hotter the fluid gets.

Most ATF can withstand normal operating temperatures of around 200 degrees F for tens of thousands of miles. But if the temperature of the fluid rises above 220 degrees F the fluid starts to break down quickly. Above 300 degrees, fluid life is measured in hundreds, not thousands of miles. And above 400 degrees, the fluid can break down in as little as 20 to 30 minutes and destroy your transmission!

ATF contains ingredients to improve its oxidation stability as well as other additives to reduce foaming and inhibit corrosion. Over time, the protective additives can also break down causing the fluid's lubrication properties and viscosity to change for the worse. That's why fluid breakdown is the leading cause of transmission operating problems and failure.

Most experts still recommend changing the fluid and filter every 3 or 5 years or 50,000 miles to extend the life of your transmission.

If you drive a truck or SUV and use it for heavy towing, changing the fluid every 2 years or 30,000 miles may be recommended to reduce the risk of premature transmission failure.

How To Change Your Transmission Fluid

The "old fashioned" way to change ATF is to drop the pan, drain the transmission, replace the filter, reinstall the pan and refill with fresh ATF. Though better than nothing, this approach can leave up to two-thirds of the ATF trapped inside the torque converter (unless the converter has a drain plug, which few do).

A better approach is to take your vehicle to a shop that has a "Fluid Exchange Machine". The equipment attaches to the ATF oil cooler lines or the filler tube to exchange new fluid for old. This approach will replace all of the old fluid.

IMPORTANT: When you refill the transmission with new fluid, be sure to use a CLEAN funnel. Wipe the funnel and make sure there is no dirt, lint or motor oil residue inside the funnel. Any dirt or other contaminants in a dirty funnel can cause problems if it gets inside your transmission!

The filter inside the transmission should also be changed when the fluid is changed to get rid of trapped contaminants. A plugged filter can cause the same kind of problems as a low fluid level or low line pressure.

Always use the type of ATF specified by the vehicle manufacturer. If you don't know, refer to the owners manual or a reference chart. The type of ATF may also be specified on the transmission dipstick.

Different Types of Automatic Transmission Fluid

The following is a summary of the many different types of ATF:

WARNING:Make sure you choose the correct fluid for your transmission. Using the wrong fluid may cause transmission problems and damage.

AW1 -- Special ATF for 2011-12 Buick Regal, 2010-12 Cadillac SRX with AF40 6-speed automatic, also certain 2006 and up Saab and Volvo models with Aisin Warner TF-80SC 6-speed transmission, and Ford models with AW F21 6-speed transmission. The GM part number for this fluid is 19256039.

Type F -- Introduced by Ford in 1967 for their automatics. Also used by Toyota.

Type CJ -- Special fluid for Ford C6 transmissions. Similar to Dexron II. Must not be used in automatics that require Type F. Can be replaced with Mercon or Mercon V.

Type H -- Another limited Ford spec that differs from both Dexron and Type F. Can be replaced with Mercon or Mercon V.

Mercon -- Ford fluid introduced in 1987, very similar to Dexron II. Okay for all earlier Fords except those that require Type F. As of July 1, 2007, the production and licensing of Mercon ATF by Ford ends. Ford says applications that require Mercon ATF can now be serviced with Mercon V. See Ford TSB 06144 for more information.

Mercon V -- Replaced Mercon. Introduced in 1997 for Ranger, Explorer V6 and Aerostar, and 1998 & up Windstar, Taurus/Sable and Continental. This is the current ATF for most late model Ford products. See Ford TSB 06144 for more information.

Mercon SP -- Friction-modified ATF for Ford TorqShift Transmissions only (6HP26, 6R60 &6R75). Do NOT use in transmissions that require Mercon or Mercon V. See Ford TSB 06144 for more information.

Mercon LV -- For 2003 & up TorqShift 5R110 transmissions, 2009 and up 4R75WE and 6R80 TorqShift transmissions, and 2011 and up 6R140 TorqShift transmissions. Also 2000 and up 4F27E automatic transaxles, 2009 and up 6F35N and AWECVT transaxles, 2010 and newer 6F50N and 6F55N transaxles, and 2013 and up HF35 hybrid transaxles.

Dual Clutch Transmission Fluid (Ford) -- Special fluid for 2011 and newer DPS6 Dual Clutch transaxle.

Dexron -- General Motors original ATF for automatics.

Dexron II -- Improved GM formula with better viscosity control and additional oxidation inhibitors. Can be used in place of Dexron.

Dexron IIE -- GM fluid for electronic transmissions.

Dexron III -- Replaced Dexron IIE and adds improved oxidation and corrosion control in GM electronic automatics.

Dexron III (H) -- Improved version of Dexron III released in 2003.

Dexron III/Saturn -- A special fluid spec for Saturns.

Dexron-VI -- Introduced in 2006 for GM Hydra-Matic 6L80 6-speed rear-wheel-drive transmissions. Dexron VI now replaces Dexron III and II, and can be used in GM or import transmissions that formerly specified Dexron III or II.

Chrysler 7176 -- For Chrysler FWD transaxles.

Chrysler 7176D (ATF+2) -- Adds improved cold temperature flow and oxidation resistance. Introduced 1997.

Chrysler 7176E (ATF+3) -- Adds improved shear stability and uses a higher quality base oil. Required for four-speed automatics (do NOT use Dexron or Mercon as a substitute).

Chrysler ATF+4 (ATE) -- Introduced in 1998, ATF+4 is synthetic and replaces the previous ATF+3 fluid. Used primarily for 2000 and 2001 vehicles, it can also be used in earlier Chrysler transmissions (except 1999 and older minivans with 41TE/AE transmission). ATF+3 should continue to be used for 1999 and earlier minivans because of the potential for torque converter shudder during break in.

NOTE: Chrysler ATF+4 Must always be used in vehicles that were originally filled with ATF+4. The red dye used in ATF+4 is not permanent. As the fluid ages it may become darker or appear brown in color. ATF+4 also has a unique odor that may change with age. Therefore, do not relay on the color and odor of ATF+4 to determine if the fluid needs to be changed. Follow the OEM recommended service interval.

Chrysler ATF+5 for 2002 and newer models.

Import Vehicle ATF Applications:

BMW LT7114l or LA2634 -- Special formula for BMW transmissions.

Genuine Honda ZL ATF -- Special ATF for Honda automatics (except CVT applications).

Mercedes Pentosin ATF 134 FE (Blue) -- For the latest generation Mercedes-Benz 7-G Tronic Plus (NAG II+) automatic transmissions.

Mercedes Pentosin ATF 134 (Red) -- For Mercedes-Benz 4, 5, and 7-speed transmissions up to June 2010.

Mitsubishi Diamond SP-II & SP-Ill -- Special formula ATFs for Mitsubishi transmissions, also Hyundai and Kia.

Nissan HP/J-Matic -- Special formula for Nissan, Infiniti and some Subaru transmissions.

Nissan CVT fluid -- Special fluid for CVT transmissions.

Toyota Type T, T-III & T-IV -- Special formula ATFs for Toyota, Lexus and Scion transmissions.

What About so-called Universal ATF Fluids for all makes/models of Transmissions?

There are a number of aftermarket synthetic ATF fluids that claim to meet numerous OEM requirements. Although not exactly "universal" ATFs, they can be safely used in a variety of different applications. Such products are available from Castrol, Valvoline and others. Refer to the product label for approved applications. Make sure the product meets the specific OEM requirements for your transmission. The label on the product should list which OEM performance specifications it meets or which applications it has been "approved" for use. Do NOT use the product if it does not specifically say it meets the requirements for your transmission.

MJ-325: -- MITASU low viscosity synthetic ATF for multiple late model vehicle applications that have sequential electronically controlled automatic transmissions. The maker of this ATF says their product meets the following performance requirements for the following:

On an older High Mileage application, Will Changing the ATF Cause Problems?

Flushing out the old ATF and replacing it with new fluid should prolong the life of a transmission provided the fluid has been changed fairly regularly, say every 50,000 to 60,000 miles (or according to the OEM service interval recommendations).. But if the transmission on an older high mileage vehicle (say over 100,000 miles) has never been flushed, it's probably best to NOT flush the fluid. Here's why: The detergents in new ATF may loosen up accumulated crud inside the transmission, which could cause some problems within a few thousand miles or so after the flush. So if your fluid has never been changed and your vehicle has a lot of miles on it, it is probably best to just leave the fluid alone and top off the fluid level as needed if it is low.

Ford Engineers Recommend Against One-Size-Fits-All Automatic Transmission Fluids

Engineers at Ford Motor Company say there is no one-size-fits-all-solution for automatic transmission fluids. The company says Ford transmissions are designed for use in many different service environments and operating conditions, and each transmission has its own set of fluid requirements. All Motorcraft Automatic Transmission Fluids (ATF) have specially formulated properties to meet unique requirements that result in optimal vehicle performance, something that cannot be achieved with just a single product on the shelf.

Motorcraft has boiled down their ATF offerings to eight fluids that service technicians and motorists can use to service all Ford and Lincoln vehicles. While the aftermarket may say there is a one-size-fits-all solution ("universal" ATF), each transmission needs the correct fluid to function properly.

Current Motorcrafts Automatic Transmission Fluids include:
Continuously Variable Chain Type Transmission Fluid
Premium Automatic Transmission Fluid
FNR5 Automatic Transmission Fluid
Dual Clutch Transmission Fluid
Type F

Ford engineers do NOT recommend adding cleaners, conditioners or other performance enhancing products to these ATFs. Specially designed performance additives are already included in Motorcraft ATF formulations, making additional additives unnecessary. Aftermarket additives do not prolong the life of the fluid or the transmission, and can mask transmission symptoms without providing a cure, says Ford.

transmission fluid More Automatic Transmission Articles:

Automatic Transmission Fluid & Filter Service

Diagnosing Automatic Transmission Complaints

Automatic Transmission Service

About Electronic Automatic Transmissions

Chrysler 45RFE Automatic Transmission Shift Problems

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