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The Non-Mechanic’s Guide to Understanding the Transmission Fluid Change

Automatic transmission fluid is that mysterious fluid that sounds like it must reside in your vehicle’s transmission. It is red in color, smells kind of sweet (trust us… you don’t want to actually taste it) and, for those truly interested, is a petroleum-based fluid.

But what does transmission fluid actually do, why do you need to have a transmission fluid change and why does any of this matter? The short answer is simple – transmission fluid is the lifeblood of your transmission.

But the long answer is a bit more drawn out and technical – and that’s precisely what we’re about to get into! There are plenty of less than reputable and knowledgeable oil and lube shops that will blindly recommend a transmission fluid change. Truthfully, you DO need aperiodic transmission fluid change. However, understanding how it all works together will help you know you really need that change and when someone’s looking at your wallet as an easy target.

The Non-Mechanic’s Guide to Understanding Transmission Fluid Using Super Soaker Water Guns

An automatic transmission operates through the use of hydraulic fluid – We will shorten this to ATF (automatic transmission fluid).

To simplify the definition of a hydraulic fluid, let’s picture a super soaker squirt gun – You fill it with water, and apply pressure to it by pumping it up. When you pull the trigger, a powerful blast of water is emitted that travels 15-20 feet, and hopefully, hit the desired target.

Highline Car Care Transmission Flush - Mesa, Arizona

A transmission is operated by the same concept.

Fluid is pressurized, and then a trigger (or electronic switch) directs the ATF to its intended target. This ATF then runs through a handful of different hydraulic circuits, switches, valves, and clutches in order to make your transmission shift correctly.

If you were to look at a diagram of the path your ATF takes just to get your vehicle up to speed on a freeway on ramp, it would look like one of those mazes we used to solve as children.

Moving A 4,000 Pound Vehicle Forward at 70 Miles Per Hour

The result of all of these mechanical components operating together to propel a 4,000 lb vehicle 70 miles per hour down the freeway is HEAT (which is something we’re not short of here in Mesa, Arizona).

Without going too far into Isaac Newton’s laws of physics (mechanics deal with a bit more than you thought, yes?), let’s say this – it takes a lot of effort to keep an object this heavy in motion, which results in heat which must be dissipated.

Highline Car Care Transmission Flush – Mesa, ArizonaIt is the responsibility of your ATF to keep these components at a safe temperature by both lubricating and cooling the transmission.

Your ATF is pressurized, goes through the transmission to do it’s job and is then sent out of the transmission and into your radiator to be cooled. Once it is cooled, it is pulled right backinto the transmission and put back to work. This cycle goes on and on AND on, every time you drive your vehicle.

Transmission Fluid Change – Why It Has to Be Done

So to recap, what we have here in ATF is a fluid that is responsible for the function and also the lubrication and cooling of your vehicle’s transmission.

Sounds like a pretty busy little fluid, right?

Well, over time, this ATF will become contaminated in two manners. First, it will become contaminated with metal and friction material that is shed from your transmission through normal usage.

Second, it will be contaminated with moisture (as a fluid constantly heats up and cools off, it will collect small amounts of water through condensation).

The first is obvious, and doesn’t demand much explanation – a fluid that is contaminated with debris cannot properly lubricate.

Even though we are a Mesa auto repair shop, we want to take you to the beach for a moment.

Highline Car Care Transmission Flush – Mesa, ArizonaPicture putting on sunscreen at the beach, but you have a little sand on your arm. That sunscreen doesn’t feel very nice, does it? The sand is scratching your skin as you rub the sunscreen in. Similarly, contaminated ATF will scratch the internals of your transmission and can cause parts to fail over time.

The second might demand a bit more explanation. When ATF becomes contaminated with moisture, better known as water – A chemical reaction will occur on a microscopic level (breaking out the big guns of science now). Water and oil will create acid. Once we have acid in your ATF, it can corrode your transmission’s metal internals. Transmission fluid changes are necessary.

How much should a transmission fluid change service cost?

This is a very subjective question, as many shops will offer different types of services.

Some will simply drain and fill your transmission which only replaces maybe 40% of your transmissions fluids. Others will do a transmission filter service, which replaces your transmission’s filter and approximately 40% of its fluids. Others yet will offer a transmission flush which incorporates a flush machine and will exchange approximately 90% of your fluids. Some shops will do a fluid flush AND a filter change.

On top of that, different manufactures require different types of fluid, that vastly vary in price. All of this aside, the short answer is that a transmission fluid service may run you anywhere from $99, all the way to $400.

Transmission Repair at Highline Car Care

Should you have a question as to which service is best for your vehicle and what it will cost, we recommend calling Highline Car Care for advice.

Highline Car Care, Mesa Arizona, Transmission Change and Flush

Everything described above is true of every car across the globe with an automatic transmission across.

In Arizona, the contamination of your transmission fluid is exacerbated. A reputable Mesa auto repair shop will recommend an transmission fluid change, also know as a  flush or “exchange”, every 60,000 miles.

Any recommendation at a significantly lower milage interval and you may want to get a second opinion. A recommendation at a significantly higher mileage interval and a mechanic is not doing their job.

We’re located in the heart of Mesa which puts us in the heart of the summer heat and a 60,000-mile interval is what we recommend for Arizona drivers (see our entire maintenance schedule here).

This will keep it fresh and ready to handle its extensive job.

And you thought ATF was insignificant, didn’t you?

Our shop, Highline Car Care, is the best option for automatic transmission flush. We have been in business since 2000 and in that time we have cared for and serviced many vehicles. We’re located west of Mesa Drive just south of US 60. You can learn more about us here and get directions to our Mesa auto shop here.

Wes Hawkins

Owner of Highline Car Care

Wes Hawkins, Owner of Highline Car Care

Wes Hawkins is the Owner of Highline Car Care in Mesa, Arizona. Highline works on all makes and models with a special emphasis placed on Toyota, Honda, Acura and other Japanese designed and manufactured vehicles.

Highline has grown from Wes in his garage doing repair and maintenance work for family and friends to their current shop located in Mesa, Arizona.


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  3. […] out our article on transmission fluid HERE for more specifics. But the bottom line is that here in the East Valley, Highline Car Care […]

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