AUTOMATIC TRANSMISSION FLUIDS

What is Automatic Transmission Fluid?

Automatic transmission fluid  also referred to as ATF, ensures proper operation, performance and protection of the automatic transmission. Also referred to as ATF, this fluid ensures proper operation, performance and protection of the automatic transmission. Critical areas of performance include the following:

• Heat resistance and thermal stability, helps prevent deposit and sludge from forming as the result of the high temperature operation of the transmission
• Frictional Characteristics enables smooth gear changes by supplying the correct friction to the transmission clutches and bands
• Extreme pressure/load carrying performance ensures anti-wear and gear durability
• Viscosity stability helps maintain viscosity or proper fluid thickness over a wide temperature range
• Low temperature flow ensures effective operation of hydraulics and electronics controls at low temperature

What kind of automatic transmission fluids are there?

There are 3 basic types of automatic transmissions found throughout the world.  

• The Dual Clutch Transmission (or DCT)
• The Continuously Variable Transmission (or CVT)
•  The step-type transmission which is the most common, especially in the US.  

There are several main components that make up the step-type transmission. The pump supplies pressurized transmission fluid for many uses throughout the unit. The planetary gear sets provide the chosen gear ratios for the vehicle. Clutches or “clutch packs” engage and disengage the gear sets. The Torque Converter connects the transmission to the engine and multiplies the torque during initial acceleration. It uses two turbines which spin independently, but which are fluid coupled allowing the engine to idle while the engine is stopped and produce smoother acceleration as it shifts through the gears. Finally, the Mechatronics is the “brain” of the transmission, a complex system of ports, valves and electronics that control all transmission functions. 

The one component of the entire system that’s critical to all of these parts working properly together is the Automatic Transmission Fluid, or ATF. It acts as a hydraulic fluid, to engage clutch packs & shift the gears. It acts as a corrosion inhibitor and wear protection for the Planetary Gear sets. It has to flow easily from minus 40 degrees Fahrenheit to nearly 400, even in fine valve assemblies. The ATF precisely controls friction in the clutch packs and maintains it throughout the drain interval which is perhaps the most important property of an ATF all while providing lubrication to hundreds of moving parts even under high temperatures and extreme pressure. So, using the right ATF is critical to the performance and long life of your transmission.

What type of ATF Fluid do I need?

Depending upon your vehicle manufacturer, model type, and model year, a specific automatic transmission fluid will be required to ensure proper transmission performance and protection. Always follow the recommendation of the vehicle manufacturer to ensure the proper fluid is used and fluid change interval is maintained. This recommendation can commonly be found in your vehicle owner’s manual.

The types of Automatic Transmission Fluids fall into a few categories:

1). OEM Approved Fluids: 

ATF Fluids are not defined by a weight as is motor oil. Rather it is defined by specification, certification or application. 

Ford, GM, and Chrysler have established their own specifications for automatic transmission fluids. For GM it is the DEXRON series of specifications with the mainstream specification being DEXRON VI for newer GM vehicles. Earlier DEXRON specifications would be acceptable for older GM vehicles. For Ford, the MERCON specification is important with the latest being MERCON LV. For Chrysler the ATF +4 specification is the latest specification.

These ATFs have been submitted for testing by the OEM and officially approved for use in the respective application. 

2). Multi-Vehicle Transmissions ATF 

Multi-vehicle transmission fluids have become popular and these may carry GM, Ford and Chrysler certifications but also be suitable for use in Japanese and European vehicles.

3). Continuously Variable Transmissions (CVTs) Fluid

CVTs are growing in usage to improve fuel economy. Such transmissions are common to hybrid vehicles but can be found on non-hybrids as well. CVT transmissions have continuously changing speed ratios unlike classic automatic transmissions, also known as “step transmissions,” which have distinct gear shifts. A CVT fluid should be used in this application to ensure proper performance and protection especially with the CVT push belt regarding wear protection.

4). Type F Transmission Fluid

This fluid meets old Ford specification and is not commonly recommended for today’s transmissions. This may be the fluid of choice of older Ford classic cars, racing or hydraulic applications.

 How often should I change my transmission fluid

ATF Oil Change – Proper Service Intervals

The proper time to change automatic transmission fluid will be defined in individual owner’s manuals. In many cases fluid change interval requirements will be more frequent if the vehicle is operated under severe conditions. Such conditions will be defined by the manufacturer.

Automatic transmissions are now more complex than ever, placing ever-greater demands on auto transmission fluids.  In fact, the automatic transmission is perhaps the most complicated mechanical component in an automobile.  The automatic transmission combines electrical & mechanical systems, hydraulics and computer processors to smoothly shift through the gears and transfer engine power to the drive wheels. 

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