Your vehicle has a tremendous amount of different fluids that do many different jobs for many different parts.
You probably know a little about engine oil and that it needs to be changed on a regular basis, depending on loads of different factors. You’ve probably also heard about transmission fluid, but likely have much more limited knowledge about it.
Just like engine oil, transmission fluid has lubricating and cooling qualities that allow moving components to function correctly. Also, just like engine oil, it breaks down over time, gets dirty, and needs to be changed.
Even vehicles with manual transmissions contain some form of oil within them, though the oil can be different than automatic transmission fluid.
Regardless of what type of transmission your vehicle has, it’s especially important to make sure that its oil is regularly changed to prevent excess wear and eventual major damage.
Repairs for this are expensive and could end up costing thousands, so this is definitely not something you’ll want to get yourself into.
Let’s look at how often you should change your transmission fluid, as well as why it is important to do so.
What Does Transmission Fluid Do?
Regardless of whether your vehicle has an automatic transmission or a manual one, this fluid acts as a lubricant.
Both systems have moving gears, synchronizers, and bearings. All of those parts move as the vehicle moves forward, and lubrication keeps them moving smoothly.
In turn, this also prevents excess heat buildup. Like an engine without oil, your transmission would overheat from the friction from all its gears, and it could be destroyed.
An automatic transmission also uses automatic transmission fluid as a viscous coupling to actually make your vehicle move forward.
In short, this fluid is forced through various components within a torque converter with pressure to make your vehicle move faster or slower depending on the amount of pressure the fluid provides.
The process is much more complicated than that, but it’s quite similar to how a windmill works. The harder the wind blows, the faster the windmill turns.
Why Should You Change the Transmission Fluid in Your Vehicle?
Now that you know what this is and what it does exactly, you have a better idea about just how important it is to your transmission’s health.
The following list will discuss some of the most important reasons why you should make sure to perform this task frequently enough.
It Deteriorates and Gets Dirty like Oil
Regardless of how good your transmission fluid is, it will break down with usage. Additionally, it gets dirty from gear wear caused by friction, especially within a manual transmission.
Over time, tiny pieces of metal and contaminants will accumulate within the transmission pan, making its lubricating qualities less effective. Heat from moving components will also cause it to break down over time.
Proper Cooling Can Be Prohibited
With this breakdown also comes the inability of the fluid to cool the transmission correctly.
A good rule of thumb to follow is this: The cleaner the transmission fluid, the more it can dissipate heat and prevent damage from occurring.
Shifting Could Be Affected
Because automatic transmissions rely on their fluids to create vehicle movement and proper shifting, keeping that fluid clean will allow your transmission to function properly.
Dirty or old fluid could cause your vehicle to shift erratically, or not at all.
If a leak is present and fluid is lost, changing or adding fluid at the correct time could save you from being stranded on the side of the road.
Leaking Could Occur
One of the lesser known transmission fluid duties is that it conditions seals, gaskets, and components within the transmission itself.
As it breaks down and gets dirty, its conditioning properties also break down, and leaking could occur as a result.
Keeping your transmission fluid clean will prevent premature aging, and will promote longer transmission life with fewer opportunities for seal leaking.
How Often Should You Change Your Car’s Transmission Fluid?
Technology and variances in how vehicles are designed have contributed to a wide range of suggested intervals.
Despite this, there are still three main suggested fluid change intervals applicable to most vehicles today.
As always, though, checking your owner’s manual will give you direct instructions on exactly when your vehicle needs this task done, as well as how to do it.
30,000-60,000 Miles
30,000 to 60,000 mile intervals are still recommended today for some vehicles, but are slowly becoming a thing of the past.
This interval is mostly reserved for older vehicles, manual vehicles, vehicles which frequently tow large loads, and other “special use” vehicles like taxis which are subject to unusually extreme driving conditions.
Some manual vehicles that are used to towing heavy loads have a suggested interval less than 30,000 miles, but with only about 5% of vehicles sold today having a manual transmission, this interval is unlikely to be encountered.
50,000-100,000 Miles
The 50,000-100,000 mile change interval is much more common in most cars today.
Even manual vehicles are able to go farther with modern gear oils than they used to back in the day, and even vehicles used for towing are beginning to push the 50,000 mile mark because of more advanced technology and better formulas.
Currently, most manufacturers and mechanics suggest that transmission fluid is changed at some point between 50,000 and 100,000 miles, depending on your vehicle and type of driving.
100,000 Miles to Never
The newest vehicles designed these days tend to require less frequent changes, with some not even having a section in the owner’s manual for fluid change intervals at all.
Most mechanics don’t recommend not having the transmission fluid changed at least once every 100,000 miles, though, but some vehicles’ owner’s manuals don’t even contain a section about such changes altogether.
This is especially common in complex vehicles such as BMW and Mercedes models.
Watch the following video for more information about when and how often your vehicle might need this maintenance task done:
What Factors Affect How Often You Should Change Transmission Fluid?
There are a few reasons you should consider changing your transmission fluid sooner than suggested, and most of those involve extreme driving conditions.
Vehicles which tow and haul heavy loads consistently are recommended to have their transmission fluid changed more frequently than those which don’t. Most owner’s manuals will provide specific instructions for this type of situation, and can even cut the intervals in half.
City driving, stop-and-go commuting, and situations where long periods of idling occur will require more frequent changes, too.
This has to do with more frequent transmission gear changes and increased heat within, both of which break down transmission fluid faster than normal.
Extreme climates with large temperature changes can even affect how often you should consider performing a change as well. This won’t affect the transmission fluid as much as extreme driving conditions, but it should be considered (and fluid monitored more closely).
What Are Some Warning Signs That a Replacement is Overdue?
If you have neglected to perform this task for a while now while you should have done otherwise, your vehicle will often provide you with some obvious warning signs that it needs to be changed right away.
Your Vehicle Is Shifting Abnormally or Not at All
Just because your vehicle is shifting erratically or not all doesn’t always mean that transmission failure is imminent.
A transmission fluid change is often able to rectify this problem, especially if the fluid has degraded and can’t function properly.
Your Vehicle Shifts out of Gear
A similar sign that it’s time for this car maintenance task is if your vehicle slips out gear while driving. This might be slight slipping or a total loss of gearing.
Any abnormal shifting or slipping that occurs should be addressed immediately, as damage could occur or you could find yourself stranded on the side of the road.
Overheating
Transmission overheating most often occurs because of a lack of transmission fluid rather than one that’s been degraded. However, this isn’t always the case.
Extreme driving conditions and not performing frequent enough changes will often result in this overheating.
This could cause the check engine light to flash or illuminate, which makes it easier to diagnose the issue.
You Hear Grinding Sounds
Transmission gear grinding could result from the lack of lubrication the transmission fluid provides.
If you hear grinding or other noises coming from the transmission, it might be time to replace the fluid.
The Shifter in Your Manual Vehicle Doesn’t Feel Right
If your vehicle has a manual transmission, you should normally be able to shift quite easily.
If there is unusual effort needed to shift or the shifter doesn’t feel right, you might need to get the gear oil changed.
How Do You Know When Your Transmission Fluid Doesn’t Need to Be Changed?
There are several ways to check whether or not a change is actually needed, just for the sake of double checking and making sure you’re not wasting your time and money on something that isn’t even required at this point.
Even if a mechanic suggests that this task needs to be done, you can look for some signs that will tell you it can wait.
You can often check the transmission fluid by examining the dipstick, much like you would check the oil in your vehicle.
Is it Dirty?
If your transmission fluid doesn’t contain visible particles, it is mostly clear, and you can’t see shiny pieces with the fluid, you shouldn’t have to change it.
What Color Is It?
Transmission fluid comes in many different colors, but most automatic fluids come in a red or pink color.
Manual transmission fluid might be the color of regular oil, but many manual transmission vehicles also use automatic formulas just fine.
As long as it isn’t milky, dark brown, or black, you should not have to replace it.
Does It Have a Burnt Smell?
One telltale sign that it needs to be replaced is when it smells burnt.
If you can’t detect this when checking the fluid, you won’t have to change it.
Is It past the Change Interval Recommended by Your Owner’s Manual?
The manufacturer of your vehicle knows what’s best for it.
If it is within normal parameters for a suggested transmission fluid change, you probably won’t have to worry about this unless your vehicle’s behavior (or any other unusual symptoms that may arise) suggests otherwise.
Are There Any Other Tips I Should Know About?
The golden rule of any automotive maintenance questions, vehicle operations, or correct product usage is to reference the owner’s manual. This is especially important if you own a vehicle with a manual transmission.
Manual transmission vehicles can use a variety of different transmission fluids, including automatic formulas.
Your owner’s manual will also tell you the correct interval for the type required on both automatic and manual vehicles.
Some transmissions have filters that can be changed when transmission fluid is changed. If your owner’s manual specifies to change the filter with the transmission fluid, then it’s very important that you don’t forget (or neglect) to do so.
Some of the newest automatic transmissions contain long life transmission fluid which is reported to last the lifetime of the transmission.
These transmissions often don’t contain a way to monitor fluid levels except through an OBD II reader (click here for the best OBD II code readers) or transmission scanner.
Also keep in mind that there is no harm in performing this change sooner than what is recommended, as long as you’re not doing so for no justifiable reason at all.
If you recognize the signs of degradation, change it as soon as possible so that larger problems don’t arise down the road – ones that will cost you loads of time and money.
With that being said, many claim that performing a change when it’s well overdue could actually cause more harm than good. Holes and leaks could actually be plugged by gunky and old transmission fluid, and changing it might clean out those holes, causing leaks.
This has happened in the past, causing transmission failure, but there isn’t any conclusive evidence yet to prove that changing bad transmission fluid will actually cause its destruction.
Wrapping it Up
So, as you’ve clearly seen by now, all of this plays a small (but vital) role in keeping your vehicle moving and not breaking down.
Changing the fluid at the correct mileage as presented in your owner’s manual will provide you with the best possible experience you can have.
Just like other fluids in your vehicle, transmission fluid gets dirty and wears out. When that happens, it is no longer effective.
Without proper lubrication, heat dissipation, and shifting ability, your transmission could wear out prematurely or completely fail, leaving you with a hefty repair bill.
Your owner’s manual holds the key to a long-lasting, healthy transmission and will tell you exactly when you need to have your transmission fluid changed.
So, make sure you listen to the experts that manufactured your vehicle before you listen to anybody else’s suggestions!
