Fluid Exchanges, Part 2

Exchange vehicle fluids on a schedule recommended by the manufacturer to keep your car in the best condition possible.
Here are tips on changing your vehicle fluids.

What You Need to Know about Automatic Transmission Fluid

Automatic transmission fluid is made in many different formulations, not only for different vehicles, but also in many cases because newer models of the same vehicle may require new, updated fluid for proper operation; this means that the new fluid may or may not be backwardly compatible. That also means you may not be able to use the newest fluid in your older vehicle.

Transmission fluid exchanges usually start by installing a quart of “cleaner” in the transmission, and running the engine for a specified time to loosen varnish and deposits. Then the exchange equipment is connected, and new fluid is pumped through the system, forcing out the now-used cleaner along with the old transmission fluid, dirt, and contaminants.

Servicing the automatic transmission fluid when recommended is critical. As the transmission fluid ages, it accumulates more dirt (as it is designed to do) and the additives are depleted. These combined effects of aging affect the heat-carrying ability of the fluid, and your transmission may overheat and consequently fail. The excess dirt also may clog the small passageways in the transmission cooler (a small “radiator” for the transmission), and hasten premature failure.

What you Need to Know about Power Steering Fluid

The most popular steering system in modern vehicles is the “rack and pinion.” It is lighter and more efficient than the center-link/steering gear box system used in older vehicles and many light trucks. The fluid that powers this hydraulic system, not surprisingly named “power steering fluid,” also performs functions such as cooling the system and holding in suspension abrasive dirt and other debris. Because the engines in most new vehicles run hotter than those of older generations—part of the engineering effort to improve efficiency—the extra heat under the hood also works, over time, to shorten the effective life of the power steering fluid.

So, when recommended by your owner’s manual or when chemical testing (dip strips) show additive depletion, the money spent replacing the fluid should be considered as proactive protection of your investment. It is insurance against preventable failures.

What You Need to Know about Brake System Fluid

Brake fluid’s most important function is hydraulic; that is, assisted by a pump that increases the force so you don’t have to push so hard, it transmits the pressure you apply to the brake pedal, through a master cylinder and maybe an anti-lock braking module, to the brakes at each wheel.

Brake fluid wears out over time as it accumulates moisture, and as corrosion inhibitors are depleted. Almost every brake fluid (labeled by Department of Transportation grading such as DOT 3, DOT 4,) is “hydroscopic,” meaning it readily absorbs moisture from the air. The formulation of DOT 5 makes it immune to this part of the aging process. And make sure, if you ever do it yourself and top off the fluid, that you use the right fluid. Your local shop can check the quality and expected remaining lifespan of your brake fluid with a quick chemical test and analysis.

What You Need to Know about Differential Fluid

The differential on rear-wheel-drive vehicles, sometimes called the “pumpkin” because it looks like one, transfers the engine power coming out of the transmission by means of the drive shaft, to the rear wheels. On front wheel drive vehicles the differential is there, right in front by the engine.

This unseen differential fluid works very hard for you, and never even gets a thank you in return. When clean and new, it helps reduce wear in the differential, and reduces the heat that is the enemy of most mechanisms. For smooth, trouble-free operation, service this important component by changing the differential fluid as recommended in your owner’s manual.

Limited slip differentials (which do just that, limit the slip of power to the wheels) are often an option on high–performance vehicles require a special fluid or one that is modified by a manufacturer-approved additive.

Discover why maintaining a regular schedule of changing vehicle fluids is so important.

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