Can Changing Your Transmission Fluid Cause Damage?

You may or may not know that your car’s transmission contains fluid that is designed to be replaced just like engine oil is meant to be replaced at certain intervals.  Neglecting to change the transmission fluid in your transmission can have negative consequences on the transmission and can reduce the lifespan.

But is it always a good idea to change your transmission fluid and can changing your transmission fluid cause damage?  If your transmission fluid has never been changed before replacing the transmission fluid can cause the transmission to start slipping, even if the transmission wasn’t slipping before.  That’s because old transmission fluid will contain clutch material that may actually be helping the transmission shift gears.

With that said how do you know if you should change the transmission fluid in your car?  How often should you replace the transmission fluid in your car to keep these sorts of issues from happening?  Keep reading to find out.

Can Changing Your Transmission Fluid Damage The Transmission?

Changing your transmission fluid cannot cause any damage by itself, if everything is fine inside of your transmission then everything will be fine when you change your transmission fluid.  Where you start to run into issues when you change your transmission fluid is when your transmissions clutch packs are already worn down from use.

If you go and replace your transmission fluid when your automatic transmission clutch packs are worn down this can cause your transmission to start slipping.  This is because the old transmission fluid will contain clutch pack particles that will actually help the transmission shift.

The clutch pack materials floating around in the transmission fluid will make the transmission fluid grittier than brand new transmission fluid and will allow the clutch packs to grip better.  Since new transmission fluid will be clean and not have any clutch material floating around in it the clutch packs sometimes won’t be able to grip as well causing the transmission to slip when changing gears.

So while the new transmission fluid may cause your transmission to start to have issues, in reality, the issues with the transmission were already there you just brought them to light by changing out your transmission fluid.

Should You Change Transmission Fluid On an Unmaintained Car?

As the transmissions in vehicles are used particles of the clutch or clutch packs will begin to accumulate in the transmission fluid.  These particles and debris are meant to be flushed out of your transmission when you drain your old transmission fluid. But if you don’t ever drain your transmission fluid the debris and clutch particles will remain circulating throughout the transmission.

While these particles won’t damage the transmission themselves they may actually contribute to allowing the transmission to shift properly as the transmission keeps piling on the mileage.

Once your transmission fluid gets old enough and your clutch packs wear down the excess clutch material can help the transmission shift gears.  This is why you may want to think twice about changing your transmission fluid if you have an older transmission that has been running the same transmission fluid for a long time.

Just because the transmission hasn’t been maintained doesn’t mean that changing the transmission fluid in it will cause it to start slipping.  But it’s a common enough occurrence that a lot of mechanics will warn against changing out the transmission fluid on a transmission that has not ever had the fluid changed.

Should You Change Transmission Fluid On a Maintained Car?

As long as you change your transmission fluid periodically you don’t have much to worry about when it comes to causing harm to your engine.  Transmission fluid is designed to be replaced periodically so it’s a good idea to keep up with the maintenance schedule defined by the vehicle manufacturer, especially if your car is still under warranty.

Deciding not to change the transmission fluid at the specified interval determined by the vehicle manufacturer can void your warranty if you still have one left on your vehicle.  That’s why it’s important to keep up with the maintenance schedule specified by your vehicle manufacturer, especially while your vehicle is still under warranty.

What If I Don’t Know the Last Time The Transmission Fluid Was Changed?

Let’s say you bought a car and you don’t know if the transmission fluid was ever changed on it before.  Should you change the transmission fluid on the vehicle or should you leave the transmission fluid alone?  Really it depends on when the last time the transmission fluid was changed.

1. Ask For Service Records/Carfax

First, you would want to check for any maintenance history indicating that the transmission fluid was changed previously.  Service history from various dealerships or mechanics is good news and indicates that the vehicle was maintained by the previous owner.

However, if the car doesn’t have any previous service history it doesn’t mean that the car wasn’t serviced, the previous owner may have performed their own maintenance on the car.  But it could also be the case that the previous owner didn’t really maintain their car all that well.

That’s why it’s a good idea to ask the current owner if they have any service records for their car before buying it.

2. Inspect Transmission Fluid

It’s a good idea to inspect the current state of the transmission fluid at this point before moving any further.  Your car should have a dipstick to check the transmission fluid levels, you would want to pull out the dipstick to check the transmission fluid levels to make sure that they are within range and are not too low or that it’s overfilled.

As you are checking the transmission fluid levels you would want to inspect the color of the transmission fluid with a paper towel or cloth (white paper towels are preferred because you will want to inspect the color of the fluid). Your transmission fluid should be a bright red and should be translucent or easy to see through.

If your transmission fluid is bright red and clear this indicates that your transmission fluid is clean and has likely been replaced recently. If your transmission fluid is dark red, dark brown, or looks like it has a lot of particles floating around in it then it’s likely the transmission fluid is older and it hasn’t been replaced recently.

What Should You Do If Your Transmission is Slipping Now?

There are many reasons why your transmission could be slipping and are typically attributed to the type of transmission you have.  Automatic transmissions will start to slip if they get low in transmission fluid.  With manual transmissions as the clutch starts to wear out, it will begin to slip as it fights to maintain a grip on the flywheel.

Older automatic transmissions can also start to slip after having the transmission fluid changed if it was never replaced.  Not all unmaintained transmissions will start to slip after having the transmission fluid changed but it’s common enough that a lot of mechanics warn against doing it.

Another easy and cheap fix that you can attempt before having your transmission rebuilt or replaced it to pour a transmission stop slip product into your transmission to see if that helps the situation or not.

Lucas Oil transmission fix is designed to be poured into your transmission in an attempt to keep your transmission from slipping and jerking through gears.  To check out the current prices of Lucas Oil transmission fix on Amazon click here (link to Amazon.com).

To learn more about what can cause your transmission to start slipping and what you can do to prevent your transmission from slipping in the first place check out my other article what can cause transmission slipping?

How Often Should You Change Your Transmission Fluid?

The recommended transmission change interval will vary depending on your specific vehicle manufacturer and transmission type.  As a general recommendation, a lot of vehicle manufacturers will recommend changing the transmission fluid in their cars in the 30,000-60,000 mile range.  So for most people they should have their transmission fluid changed every 3-5 oil changes.

Changing your transmission fluid before the recommended oil change will not damage your transmission and can help keep the fluid cleaner longer.  Some people change their transmission fluid after every couple of oil changes.

Just make sure that if you plan on changing your transmission fluid that you keep up with the maintenance schedule as once you stop changing your transmission fluid you may want to think twice about changing the transmission fluid again.  More on that below.

How Automatic and Manual Transmissions Use Transmission Fluid

Like I mentioned above changing your transmission fluid won’t harm your transmission directly but it can have an impact on how automatic transmissions shift.  Does the same apply to manual transmissions?

The short answer is no, manual transmissions are less reliant on the transmission fluid within them and are less likely to cause issues if the transmission fluid is changed.   Manual transmissions will still need transmission fluid in them to work properly but the transmission fluid in manual transmissions is mainly just used to keep the gears inside of the transmission lubricated.

With Automatic transmissions, the use of transmission fluid is much more important as with automatic transmissions the transmission fluid is pumped throughout the transmission and will be used to operate various hydraulics within the automatic transmission and tell the transmission when to shift between gears.  These hydraulic parts are reliant on automatic transmission fluid to be able to do their job which is why fluid levels are more important with automatic transmission.

To learn more about how the internals of automatic transmissions work check out the video below.

Since manual transmissions use your foot to operate the clutch, they don’t need the same hydraulic parts that tell the transmission when to shift between gears.  With manual transmissions, you choose when to shift between gears by pressing the clutch pedal in and then shifting gears with the gear selector.

One other thing to keep in mind,  on manual transmissions, the clutch is designed to be replaced from time to time; whereas with automatic transmissions, once the clutch packs within them start to wear down the whole transmission needs to be rebuilt.  The main difference between replacing a clutch and rebuilding a transmission is the cost to have them performed. Replacing a clutch on a manual transmission car usually costs about $1,000 while it will typically cost around $3,000 to have a transmission rebuilt.

Is It Better To Flush or Change Transmission Fluid?

Having your transmission fluid changed or flushed has been a hot topic for automotive enthusiasts for a long time. You may have heard both terms and are wondering if it’s better to have your transmission fluid changed or flushed.  If so you may want to check out my other article that talks about the pros and cons of a transmission fluid change vs a flush and which route you should go (link to article).