The Importance of Using the Proper Automatic Transmission Fluid.


The automatic transmissions found on many modern cars are complex pieces of equipment. Every piece that goes into an automatic transmission is made to very precise specifications. Even the fluid type to be used in the transmission is carefully engineered to help get the best performance and longest service life out of the transmission. It is for this reason the do-it-yourself type of person must be careful when selecting a transmission fluid to put in his or her vehicle.

Transmission fluids are most often made of a mineral oil base. To this base various additives are added to give the fluid certain properties that the manufacturer wants. One type of additive is friction modifiers. Friction modifiers are chemicals added to the fluid to make parts that are inside the fluid slip across each other easier or harder. This friction modification is a very important function of the transmission fluid. Inside the automatic transmission are friction discs. These friction discs are called clutch packs. The clutch packs control the sifting pattern of the transmission. When the transmission reaches a pre-determined speed a clutch pack may be pressed together to turn it on or pulled apart to turn the clutch pack off. The friction modification properties of the transmission fluid help to determine how fast these clutch packs push together or pull apart. This in turn determines the feel of the shift. Using the wrong type of fluid, such as using a Ford type fluid in a Chevrolet transmission, may result in a change in how the shifting of the transmission feels or may even cause severe damage to the clutch packs or the transmission as a whole.

Another important property of automatic transmission fluid is how the fluid reacts with various materials inside the transmission. Some types of materials inside the transmission may be corroded, damaged or destroyed if the wrong type of fluid is used inside the transmission. An example of this is the material the friction sides of the clutch packs are made of. Some friction materials are a metal and paper mixture. The friction material is held onto the steel support of the clutch pack by a specially designed type of glue. This glue is designed to hold best when submerged inside the fluid that was designed for the transmission. If the wrong type of fluid is used, this glue may become weak or dissolve away completely. This type of failure would cause the loss of one or more gear ranges in the transmission and would often render the vehicle non operational.

These are just a few examples of why the proper fluid must be used inside automatic transmissions. The knowledgeable individual will always consult his or her vehicle owner’s manual before adding automatic transmission fluid to a vehicle. If the wrong type of fluid is used expensive repairs are almost always in the future.

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