How & When to Change Transmission Fluid

The best source of peace of mind in the automotive world is regular maintenance, and maintaining your transmission fluid is one of the most important parts. An automatic transmission uses fluid for two purposes: to provide lubrication and cooling for certain gears and components, and also to provide the proper amount of friction for the clutch packs in the transmission to operate properly, and keep cool.

While the industry has done a great job training vehicle owners about the necessity of the engine oil change, these same owners still often neglect the transmission fluid, often until it’s too late. Over time, transmission fluid loses its ability to properly lubricate and keep the transmission cool, and an overwhelming amount of transmission failures are due to neglect of fluid.

It is crucial to know when to change your transmission fluid, how to check your transmission fluid, and the costs of changing the fluid if you take the vehicle to a professional. You have the option to change that transmission fluid and its parts with no labor costs associated with it or with the confidence of handing the job to a professional.

When to Change Your Transmission Fluid

When to change your transmission fluid comes at the behest of a few factors. Some factors include the climate, the fluidity of traffic, towing, and other concerns that can affect the fluid’s longevity. Hence, how often to change transmission fluid will vary according to the vehicle and its frequency of use.

Many manufacturers in the 1990’s and early 2000’s began developing synthetic and specific-type transmission fluids, and with this, extended the service life of the fluid, sometimes even declaring a “lifetime fluid”.  In retrospect, this led to many transmission failures due to the continued neglect of the fluid. As transmission fluid begins to degrade, the temperature inside the transmission will get higher during operation, leading to further breakdown of the fluid, which leads to failures such as clutch pack slippage, banging or knocking going into gear, pump failure, and ultimately, transmission failure.

A common, one-size-fits-all recommendation for when to change your transmission fluid is every 30,000-40,000 miles, or 5 years, based on normal, everyday driving. Truck owners who do frequent towing, or constant stop/start city drivers need to move this interval into the 20-25,000 range. Like engine oil, changing transmission fluid too much will never hurt anything but your check book.

Check your vehicle’s owner’s manual for the recommended change frequency, and also ask for recommendations within your community of ownership on car forums and the internet. Many vehicles over time become very failure-prone to transmission issues that the original manufacturer was not aware of at the time of recommendation, and changing the fluid more often will help keep the transmission operating properly.

How and Why You Should Check Your Transmission Fluid

How to change your transmission fluid

How to Check Transmission Fluid

Learning how to check transmission fluid is simple. In the majority of cases, transmission fluid is checked while the engine is running, unlike engine oil. There are some exceptions, so check your owner’s manual or online to determine.

Ensure that the vehicle is on a level surface. Next, locate the transmission fluid’s dipstick and pull it out. Wipe it clean with a clean cloth. Insert the dipstick all the way and pull it out. It will let you know the transmission fluid’s level, and you will notice its color at the tip of the dipstick. Assess its color and smell and proceed with the recommendations for service if it is determined that there is a need for assistance. Keep in mind, there are markings on the dipstick that will read “full” and “low” or “fill.” Routine checks can save a lot of money over time.

Transmission Fluid Diagnosis

Knowing the symptoms of low transmission fluid is important. In the vast majority of vehicles, there will be no indicator light that transmission fluid is low, and just like checking oil, it must be done manually on a dipstick. Once you remove the transmission dipstick, the best and safest method is dab the dipstick either on a piece of paper or your finger (make sure the oil isn’t hot!) Now, inspect the fluid:

  • A pinkish or reddish color is an indicator that the transmission fluid is in good condition. Transmission fluid has a distinct smell, but it shouldn’t smell burnt
  • If there is a pink color but looks foamy, make sure the transmission is not over-filled. This is normal is some cases, but should always be checked out
  • If there is a brown or black color with a burnt smell, your fluid is well past its life-cycle. Have it changed and make sure the transmission is checked over
  • If you notice any grit or metal shavings of any kind in the fluid, the transmission fluid needs to be changed and inspected
  • Ensure the fluid level remains at the proper level. If it gets low, it is time for an inspection to determine where the fluid is going

Understanding Types of Transmission Fluid

Transmissions today are much different than the transmissions of 40 years ago. Back then, there were only 2 types of Fluid used – Dextron/Mercon, or Ford Type F. Today, there are over 15 different variants of transmission fluids, and many manufacturers insist using on their specific fluid for the transmission. While all manufacturers will typically always recommend “their” fluid for the transmission, there are indeed many cases where the original fluid is the only option. Because of this, it is vitally important that you not only research your owner’s manual, but also check carefully online to determine what your vehicle’s transmission takes, and if there are indeed alternatives that work as well or better.

Understand as well that many vehicles come with a variety of transmissions, even within the same engine type, so it’s important to completely understand which transmission is lurking under your car. It’s also important to understand how much fluid your transmission takes in the pan, to understand how much to buy for a complete change. Many times, the specs will be listed as just “pan” and “complete with torque converter”. The latter indicates the amount of fluid needed generally when doing a complete transmission swap with an empty torque converter. For a typical transmission fluid change, you will use the spec of the pan capacity. Generally speaking, this will usually be between 3-6 quarts of fluid.

What is Flushing vs Changing Transmission Fluid?

In the last 15 years, the process of “flushing” transmission fluid has come into play, where a machine is hooked up to a transmission line, which forces the old fluid out, and the new fluid in. The benefit to a transmission flush is that you are not only replacing the fluid in the transmission pan, but also the fluid in the torque converter and transmission cooler. In a normal transmission fluid change, you are not able to remove the old fluid from the torque converter or cooler, and after start-up, this fluid will be circulated in with the new fluid you replaced. 

While the flush process seems appealing in this aspect, it’s important to understand that changing the filter and cleaning the transmission pan are crucial, and many times, a flush is performed without dropping the pan or doing either. This is often sold as a cost-saving alternative. To really get the benefits of a transmission flush, both aspects must be performed – dropping the pan, changing the filter, and then subsequently flushing out all the old fluid. When the flush process is not available, changing the transmission fluid in the pan is the best alternative.

The task of learning to change the transmission fluid in your vehicle can be a challenge in some vehicles, easier in others. The process is generally the same for most, but there are some exceptions.

How to Change Your Transmission Fluid

1. Lift Your Vehicle

Use a jack or ramps and raise the vehicle according to the manufacturer’s recommended lift points, or drive onto the ramps.

2. Find the Transmission Pan and Set Up

Locate the transmission’s oil pan and place a drip pan to catch the old transmission fluid.

3. Drain Fluid

Some transmission pans will have a drain bolt, which saves a lot of trouble. Others, you will need to loosen the bolts that will initiate the dripping of the old transmission fluid, and eventually, the pouring of the fluid out around the edge of the pan. Beware, the old fluid may be hot, and the more you loosen the bolts, the faster it begins to flow.

4. Inspect the Transmission Pan

Take the transmission pan and inspect carefully. Many pans will have a provision with a magnet stuck to it on the inside, to gather small metal particles in the fluid. Don’t be alarmed by metallic “gunk” on the magnet. This is very normal from general wear, but large metallic chunks are not normal. Clean the pan with degreaser or in a parts washer, and wipe dry.

5. Replace the Pan Gasket

Replace the transmission pan gasket and filter being sure to carefully follow the filter replacement and proper gasket placement.

6. Re-Install the Pan and Secure the Bolts

After installing the pan, tighten the pan bolts to the proper recommended torque.

7. Add Fluid

Fill your transmission through the dipstick hole (with a funnel) and leave about a ½ quart of fluid in your last bottle. Some transmissions will have a separate fill-hole, but this is rare. Some vehicles, like Land Rovers, do not have a dipstick or fill hole up top, and a fluid extractor must be used to fill. Again, owner’s manual and online will give you the best advice here.

8. Start the Vehicle and Shift

You’ll now start the vehicle, and take the vehicle into drive, then up to reverse, and back to park, waiting about 2 seconds in each spot. Repeat this process.

9. Check the Fluid Level

Now, remove the dipstick and check the fluid level. Add the additional ½ quart of fluid if needed. Once your fluid is at the desired level, repeat step 8 one additional time, to make sure that fluid has circulated through all the circuits properly, and re-check.

10. Check Your Work

Lastly, with the vehicle running, check underneath for any drips or leaks. Test drive the vehicle.

Transmission Fluid Change Cost

Vehicle maintenance can certainly cost you money, but it’s always a much better alternative than a costly $4,000.00 transmission swap. While it always depends on the vehicle, most transmission services are between $100.00 to $300.00. Generally, most of this cost isn’t always in the labor, but in the price of the fluid if you have a vehicle that takes a very specific fluid, or a lot of it.

Remember, regardless of what your owner’s manual may recommend for a transmission fluid change, this is based on regular driving. If your vehicle is used in harsher conditions or for towing, this interval should always be moved up. Also remember, getting a general assessment of the fluid is as simple as lifting the hood, removing the dipstick for quick cleaning, and insert it again to check the results’ levels, color, and smell.

If changing or flushing the transmission fluid seems like too big of a job for you to tackle, consider one of our Preferred Shops in your area that can help you do the job – or – come into AutoZone for all the parts, tools and advice you need to tackle the job!

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Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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