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Automatic transmissions are becoming more efficient every year as engineers endeavor to maximize fuel economy and reduce pollution. Some of the changes include more forward gears in conventional automatics, and alternative designs such as dual-clutch or continuously variable transmissions. As part of these changes, new transmission types often require highly specialized fluids for proper operation and a long service life.

To further complicate things, automakers often outsource components, including transmissions, from third party suppliers. While a transmission built by an automaker may use one type of fluid, a gearbox from an outside vendor may require a fluid that meets a very different set of specifications. Using the wrong fluid in a transmission can cause problems ranging from erratic operation all the way to complete (and expensive) gearbox failure.

With such high stakes, it’s important to take your vehicle manufacturer’s automatic transmission fluid recommendations seriously. Consult the owner’s manual and make sure any fluid used meets all of the applicable specifications. To make sure the work is done right, it’s always a good idea to have your car serviced by a technician who has the experience, training and up-to-date service information necessary to work on your particular make and model of vehicle.

Sealed Transmissions

Most cars with automatic transmissions have dipsticks for quick and easy fluid level checks. However, increasing numbers of newer vehicles have sealed transmission filled with “lifetime” fluid that doesn’t need to be changed until the odometer nears or passes the 100,000-mile mark. In place of a dipstick, these transmissions have service ports with threaded plugs that can be removed to check and top up the fluid level. However, unless there are external signs of transmission fluid leakage there is really no need to do so. In fact, some service plugs have paint markings that will indicate if the seal has been broken, which could void the vehicle warranty if it can be shown an improper fluid was used in the transmission.

While the use of “lifetime” transmission fluids gives the owner one less thing to worry about, it does make it more complicated for a technician to top-up or replace fluid due to leaks or service operations that result in a loss of transmission fluid. On some hybrids, checking or changing the transmission fluid requires the use of special tools and complicated time-consuming procedures.

During routine maintenance services on vehicles with sealed transmissions, most repair centers simply perform a visual check for leaks and, if none are found, report that the fluid level is satisfactory. If leaks are evident, further diagnosis and repair will be required. If you are curious about whether your car has a sealed transmission, check the owner’s manual or ask the repair shop the next time you take your car in for service.

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Causes of Fluid Breakdown

Like many other automotive components, heat is a major contributing factor in the breakdown of automatic transmission fluid over time. Some of the heat comes from routine internal friction as the transmission operates and shifts gears, but placing the vehicle under extra stress, such as trailer towing or hauling heavy loads, creates additional heat. To help minimize thermal stress in these conditions, many vehicles come with a special switch to disable the transmission’s overdrive gears when towing.

Other than heat, the internal components of your gearbox wear over time and the transmission fluid will eventually become contaminated with particulates too small to be captured by the internal filter. When the fluid becomes excessively contaminated and chemically degraded from heat it can lead to varnish deposits and other transmission problems.

Changing the Fluid

Once your transmission fluid reaches the change interval specified by your vehicle’s manufacturer, you’ll need to have a technician drain the transmission, replace its filter and refill the system with new fluid of the appropriate type. When it comes to fluid changes, you have two options:

• In a traditional automatic transmission fluid change, the technician drains the old fluid, replaces the filter and refills the system. While faster and cheaper, this procedure replaces less than half of the total fluid volume.

• In a transmission fluid exchange, the technician drains the old fluid, replaces the filter and then uses special equipment to circulate new fluid throughout the entire system, flushing out all of the old fluid in the process. This costs more, but is the only way replace all of the fluid.

No matter which option you choose, be sure to work with a service facility center that’s trained and experienced with your make and model of vehicle. If the technician uses the wrong fluid or accidentally introduces contaminants into the system, it could damage the transmission and interfere with the safe operation of your car. When it’s time to have this important maintenance work done, you can trust a AAA Approved Auto Repair facility to do the work right the first time.
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