Automatic Transmission Fluid Properties and Functions

Automatic Transmission fluid performes many functions during service: It operates the hydraulics, lubricates the moving parts, dissipates heat through the transmission cooler, and acts as the fluid medium for the torque converter. 40 years ago only two types of automatic transmission fluid were commonly used, today there are over a dozen. Vehicle manufacturers now produce and promote their own brands of fluid for transmission service. Some vehicle manufacturers do not produce their own transmissions, but instead buy them from worldwide transmission manufacturers such as ZF and Aisin Seiki. These transmission manufacturers can design one type of transmission and sell it to different vehicle manufacturers to be used in different car and truck models, providing economies of scale for both parties. The same type of transmission may require different types of automatic transmission fluid, as determined by the vehicle manufacturer. Here is more information about Automatic Transmission Fluid.

Though not often noticed, automatic transmission fluid serves four functions. First and foremost, it is used as a hydraulic fluid to operate the valves that control pressure, regulate shifting, and actuate the Pistons and servos that engage the bands and clutches. During service, all types of transmission fluids perform this job equally well in any type of automatic transmission, even those for whose its use was not intended. Because of its relatively low viscosity, only very cold temperatures affect hydraulic function, and even then only for the first couple minutes of vehicle operation. Synthetic automatic transmission fluids have better cold flow properties, so can be used to minimize any adverse effects that very cold temperatures may have on your vehicle, and do not require transmission service as frequently.

Lubrication for the moving components is also provided by the automatic transmission fluid. Due to its low viscosity, its lubricating qualities are not nearly as effective as that of heavier petroleum lubricants, such as motor oil. Transmissions are designed with this in mind, so most do not have lubrication issues. There are some manufacturers, however, that allowed inherent design flaws to persist for years; flaws that were easily correctable. This was very apparent in the Ford Taurus, whose 1986 to 1994 models had what is arguably the worst transmission at that time.Companies such as Transgo, Transtec and Sonnax have created products which correct these design flaws which Suburban uses in all its overhauls.

Transmission Cooler Installation Reduces Heat

Heat builds up within the transmission during normal service, so automatic transmission fluid is used to dissipate it through the fluid cooler. Most transmission fluid coolers are located within the engine radiator and the heat from the transmission fluid is dissipated into the engine’s coolant through a heat exchanger. On some vehicles, an additional cooler is located in front of the radiator or the air conditioning condenser coils. It resembles a very small radiator and uses air to cool the automatic transmission fluid. There is a lot of misinformation put out primarily by those who profit from the sale of automatic transmission fluid coolers, for accurate information please read about temperatures and external transmission fluid coolers.

Though rarely discussed, the torque converter is filled with automatic transmission fluid, a vital component for its operation. The torque converter is analogous to a clutch for a manual transmission. The torque converter allows you to put the vehicle into gear while stopped, without stalling the engine. You can visit this link to read more about torque converter theory.