Automatic Transmission Maintenance Guide
Austin holds a technical writing degree and has 5 years of experience working as a Technical Product Specialist at BMW. He is an avid car enthusiast who is constantly watching F1, consuming automotive content, racing on his simulator, and working on his Toyota’s and BMW’s. Austin’s technical writing skills, extensive automotive knowledge, and hands-on experience make him an excellent resource for our readers.
The automatic transmission first found its footing in production cars as early as the 1940s. At the time, automatic gearboxes were slow to shift and prone to failure. As a result, automatic transmissions didn’t truly catch on until the technology improved to a passable level in the 1970s.
Since then, the automatic transmission has dominated the consumer car industry over the older, and more involved, manual transmission. In 2022, 96 percent of Americans drive automatic-equipped vehicles, which will likely increase even more as the technology is perfected.
While automatic transmissions have eliminated a lot of the stress of daily driving, there are a few downsides. Generally speaking, automatic transmissions are more prone to failure than traditional manual transmissions. That boils down to the ludicrous number of moving parts needed for an automatic transmission to function. Automatic transmissions are often more expensive to repair as well due to their sophistication. For that reason, it is important to stay on top of automatic transmission servicing and maintenance.
In this guide, we will provide useful information about automatic transmissions and outline the best methods for ensuring that your automatic transmission will last as long as possible without any major issues or services.
Automatic Transmission Maintenance- What is an Automatic Transmission?
Before we jump into the world of automatic transmissions, we’ll talk first about transmissions in general. A vehicle’s transmission has a single, very specific, purpose: to regulate an internal combustion engine’s rotational speed. Without a transmission, the combustion that occurs inside an engine would be uncontrolled, which would eventually lead to a structural engine failure from the internal components moving too fast and producing too much heat.
How Does A Transmission Work?
A transmission controls the speed of an engine by engaging differently sized gears which only allows the engine to operate at certain speeds. Transmissions use a clutch, or multiple clutches, to engage gears. Clutches operate by grabbing and releasing a selected gear depending on how fast you are moving. The clutch is disengaged and the engine is disconnected from the engine during gear changes, or when stopped. This allows the transmission to select a new set of gears independent of the engine’s rotation.
With a manual transmission, the driver manually selects the optimal gear by engaging a clutch pedal and moving a gear selector into the desired gear position. With an automatic transmission, the entire sequence is automated through the use of hydraulic actuators, sensors, and engine management software.
In general, all transmissions follow this overall formula. All transmissions use clutches, rely on hydraulic fluid to function, and have a set of gears for multiple engine speeds.
What is the Difference Between an Automatic and Manual Transmission?
While the overall function of an automatic and manual transmission is very similar, the construction of each type is very different. Manual transmissions are relatively simple pieces of technology. They consist of a few integral parts that can be fixed and replaced independently should they break.
Automatic transmissions feature many more parts than their manual counterparts and cannot be repaired easily, as most of the complex parts are deeply interconnected.
A manual transmission typically only features a single, manually operated, clutch to select gears. An automatic transmission uses multiple clutches to select different “planetary gears,” which include a central driving gear and similar gears that orbit it.
In a manual car, you use a clutch pedal to actuate the clutch. In an automatic transmission, there is no third pedal, as the vehicle automatically actuates the clutch packs and selects a gear based on the engine speed.
Automatic Transmission Maintenance -Types of Automatic Transmissions
As automatic transmissions have advanced and evolved over the years, other forms within the automatic transmission category have arisen. In many cases, companies that focus on delivering high-performance automatic cars choose to use semi-automatic transmissions, which give the driver a bit more input about the vehicle’s selection of gears.
CVT Automatic Transmission
A CVT, or Continuously Variable Transmission, is a unique automatic transmission system that works by adjusting the diameter of the “drive pulley” in order to fluctuate gear ratios. CVT transmissions are constructed with two pulleys and a steel belt running between them. The engine receives its own pulley in the form of a “drive pulley,” which translates torque from the engine. The “driven pulley” converts the torque from the drive pulley to power at the wheels.
By adjusting the diameter of each of the pulleys that the steel belt runs across, a CVT transmission is able to endlessly vary engine speed. This is different from a traditional automatic transmission as there aren’t fixed gears that constrain the transmission’s gearing ratios.
On paper, the CVT transmission looks good. Generally speaking, CVT transmissions increase fuel economy and smooth out jerky automatic shifts. However, there are some significant drawbacks to CVT technology. Primarily, CVTs are sluggish from a standstill, are weak in terms of their torque limit, and take longer to engage programmed “stepped” gears.
DCT Automatic Transmission
DCT, or Dual Clutch Transmissions, are often said to be the best version of a semi-automatic transmission available today. The primary feature of a DCT transmission is in its name; they feature two clutches. This has a very distinct benefit as far as changing gears is concerned. Each of the two clutches in a DCT is operated independently and each controls a set of gears. One clutch is in charge of the even gears, while the other is in control of the odd gears.
In many ways, a DCT operates like two separate gearboxes in one. Each clutch is responsible for operating its own set of gears. Each clutch selects its own gear. This makes shifting gears seamless and faster than almost any other type of automatic transmission on the market. DCTs are also far more efficient than other forms of automatic transmissions, as the dual-clutch arrangement makes it so that power is never interrupted between engine and transmission.
Most enthusiasts agree that DCTs are the best form of an automatic transmission for a number of reasons. Since DCTs are able to have the next gear already selected, shifts are seamless and smooth. DCTs also provide the best fuel economy of any automatic transmission.
AMT Automated Manual Transmission
An AMT, or automated manual transmission, is perhaps the least favorable automatic transmission variant on this list. While it is one of the most common forms of automatic transmission, it is the most prone to failure, least responsive, and least efficient transmission listed here.
An AMT works by using a combination of sensors, hydraulic actuators, and ECU programming to automatically select the optimal gear for a given speed. ECUs are programmed with preset shift patterns. These dictate the proper gear by measuring the vehicle’s engine speed. The ECU then engages actuators that operate the clutch and gearbox.
The main downfall of the AMT system is its pre-programmed gearing, which is extremely unintuitive and tends to get shifts wrong. Oftentimes, an AMT will select an improper gear, which can overexert the engine or make acceleration feel sluggish.
Automatic Transmission Maintenance
As with any other part of a car, an automatic transmission needs to be looked after to ensure its longevity. Diligent transmission maintenance is arguably more important on an automatic transmission than it is on a manual transmission, as automatics rely on specific fluids to ensure that they function properly.
What is Automatic Transmission Fluid?
Transmission fluid is one of the most important elements in terms of transmission safety and reliability. It plays a vital role in the operation of an automatic transmission, even more so than in a manual transmission.
Transmission fluid in an automatic transmission has two primary purposes: to lubricate the internal components of the transmission and to create hydraulic pressure within the system. Like an engine needs oil, transmissions need a similar viscous liquid to prevent the metal surfaces from rubbing against each other directly. Without fluid, the internal heat of the transmission would cause parts to seize or meld together.
Automatic transmissions use hydraulic actuators to function. Transmission fluid allows for the build-up of fluid pressure which allows these hydraulic functions to work properly. Without transmission fluid, an automatic transmission would fail to operate. It is therefore extremely important to make sure that your transmission fluid is at an optimal level.
Choosing the Right Automatic Transmission Fluid
It is also extremely important to only use the kind of automatic transmission fluid specified by your vehicle’s manufacturer. There are five primary types of automatic transmission fluids on the market today, each with its own unique qualities.
Dexron VI / Mercon V / ATF+4
While these three types of automatic transmission fluids are not the same, they do share a similar construction and composition. Each of the three is manufactured by their own parent company, including GM, Ford, and Chrysler respectively. In general, these types of transmission fluids are best suited for the most recent automatic transmission technology and are used in everything from domestic, American vehicles, to foreign vehicles with automatic transmissions.
All three have friction reducers present, which reduce the amount of heat generated within the transmission itself. Consult your vehicle’s owner manual to make sure that these are the right type of fluid to use with your vehicle.
Multi-Vehicle Synthetic Transmission Fluid
Multi-Vehicle synthetic transmission fluid, or MVSF, is not made by a specific manufacturer or for a specific brand. Instead, it is a universal fluid for a wide range of automatic transmission types. Most MVSFs are highly developed, using the newest addictive technology to create a specialized fluid compound. As stated in its name, multi-vehicle synthetic transmission fluid is based on a synthetic oil formula. Not all automatic transmissions support the use of multi-vehicle synthetic fluid. Before using MVSF in your vehicle, consult your owner’s manual.
CVT Automatic Fluid
CVT automatics require a different fluid formula from other forms of automatic transmissions. CVTs require a less viscous fluid because of their construction. Avoid using standard automatic transmission maintenance fluid in your CVT transmission. Most manufacturers that offer CVT-equipped vehicles provide specially formulated CVT transmission fluid. If that is the case for you, it is best to stick with the manufacturer’s suggested formula.
How Often Should You Change Your Automatic Transmission Fluid?
On average, vehicles with automatic transmissions need a transmission fluid change less frequently than vehicles with a manual transmission. It is best to perform automatic transmission maintenance every 60,000-100,000 miles.
This interval is dependent on a few different factors. For drivers that drive long distances frequently, it might be necessary to flush or change your automatic transmission fluid at shorter intervals. It never hurts to replace the fluid early and it is better to heed the side of caution to ensure a long life for your automatic transmission.
How to Check Automatic Transmission Fluid
It is important to check your automatic transmission fluid at least once a month, if not more frequently. If your transmission fluid level dips below a minimum amount, damage could occur due to overheating. After around 60,000 miles, transmission fluid loses its lubricity. The process of checking your transmission fluid is very easy and straightforward. If you have ever checked your vehicle’s engine oil, the process is very similar with a few caveats.
- The first step is to park your car, leaving the engine running. Park the vehicle on a flat surface. Parking on an incline or a decline can skew the results.
- Once the vehicle is parked and running, open the hood. It is crucial that the vehicle be on, as transmission fluid expands as it warms. Read the fluid dipstick when the fluid is warm. Reading it while the engine is cold will give an inaccurate output.
- When the engine is warm and the hood is up, the next step is locating the transmission fluid dipstick. Fluid dipsticks are made from bright plastic and are well labeled. Most TF dipsticks are located towards the front of the engine in front-wheel-drive cars and towards the rear of the engine in rear-wheel-drive cars.
- The next step is to remove the transmission fluid dipstick and wipe off the fluid with a clean towel. Reinsert the dipstick. Remove the dipstick once again and check for the markings on the dipstick which indicate the “low” and “full” levels. If the fluid reaches the “full” mark on the stick, the transmission fluid is at its proper level. Add more fluid if the fluid only reaches the “low” marking, or slightly above it.
What to Look For When Checking Automatic Transmission Fluid
There are other important things to look for when checking your transmission fluid other than just the level. Checking the color and smell of the fluid is also crucial in automatic transmission maintenance.
Viscosity of the Transmission Fluid
Feeling the viscosity of the fluid can tell you a lot about the state of the transmission fluid. You can check this by lightly touching the wet end of the transmission dipstick and rubbing the fluid between your fingers. The first and arguably most important thing to look for is metal shavings or metallic flecks in the fluid. Metal shavings in the fluid indicate that damage has occurred within the transmission. Have the transmission inspected immediately if metal particles are present in the fluid.
Typically, transmission fluid gets thicker with age which isn’t a cause for alarm. However, if the fluid feels gummy or is very resistant to spreading, it’s time for a transmission fluid flush or replacement. Bubbly or sudsy fluid is also a bad sign. Using the wrong kind of fluid or overfilling it can lead to a frothy consistency.
Transmission Fluid Smell
Most new automatic transmission fluid has a slightly sweet aroma that isn’t too overpowering or pungent. Bad transmission fluid typically has a burnt smell that is immediately noticeable and potent. If a strong burnt smell is present, it could be an indication that there is internal damage to the automatic transmission. Have the transmission inspected if the fluid has a strange smell.
Transmission Fluid Color
The color of your automatic transmission fluid is another good indicator of its health. In most cases, new transmission fluid is bright red in color. As automatic transmission fluid ages, it becomes progressively darker. Old transmission fluid is usually a deep burgundy or brown color, which indicates that it will be in need of a change eminently.
If your automatic transmission fluid is extremely dark brown or black, it could indicate that the fluid is burning within the transmission meaning that the fluid and internal components are overheating. Have the transmission inspected if your fluid is extremely dark in color.
Tips To Make Your Automatic Transmission Last Longer
As with most parts of a car, there are certain preventative measures that you can take to extend the life of your automatic transmission. Obviously, the best way to ensure a long life for your transmission is regular automatic transmission service and making sure that the fluid is in good condition and at an appropriate level. However, there are a few lesser-known tips that will help extend your transmission’s life even further.
Come to a Complete Stop Before Shifting Gears
When you are in a hurry, it is easy to forget about the damage that can be caused by shifting into park, drive, or reverse without coming to a complete stop. Automatic transmissions are built from fragile components that do not respond well to erratic or violent shifting, especially while moving, even slightly. Shifting into park while the vehicle is in motion can damage the internal gears of an automatic, so it is best to avoid doing that.
Do Not Drive On Mismatched Wheels For Extended Periods
Driving on a “donut” or “space saver” for extended periods is never a good idea. It is less well-known that driving on mismatched wheels can also cause damage to a vehicle’s transmission. As the rotational speeds of different sized wheels is also different, the discrepancy in wheel rotation can be straining for an automatic transmission.
It is never a good idea to drive farther than is specified by your vehicle’s manufacturer on a space-saver tire. In addition to being unsafe from a tire rigidity standpoint, it can also be a detriment to your automatic transmission.
Make Sure Your Foot Is Completely Off Of The Brake Pedal While Driving
A lot of drivers see the brake pedal as a free footrest while driving. While it might be more comfortable, resting your foot, even gently, on the brake pedal while on the move can be extremely strenuous on both your engine and automatic transmission. Avoiding resting your foot on the brake pedal will minimize stress on your transmission, parking linkage, and your engine, ensuring they’ll last longer.
Automatic Transmission Guide Summary
The transmission is one of a car’s most important components. Without a transmission, an engine wouldn’t have a way of translating combustion into rotational energy to move your car. In today’s day and age, transmissions have advanced to a point where they do all of the hard work for us. While automatic transmissions take a burden off of the driver, they are more troublesome and complex than their manual counterparts.
For that reason, automatic transmission maintenance is vital to prevent any unnecessary headaches down the line. Checking your automatic transmission fluid can give you a good indication of the fluid’s health and volume. It is also extremely important to use the right kind of automatic transmission fluid in your vehicle.
While frequent service is the best way to prolong your automatic transmission’s life, there are other things you can do as well. Coming to a complete stop before shifting, not driving on mismatched wheels for extended periods, and not resting your foot on the brake pedal while moving are just a few ways to get a few extra miles out of your automatic.
Modern automatic transmissions have come a long way from their sluggish and lazy upbringings. Now that they are a competent competitor against manual transmissions in terms of fun, it is important to treat them right.