What Is Transmission Fluid and What Does It Do?

Many different fluids run through a car. From engine oil to radiator fluid to air conditioning refrigerants and transmission fluid, keeping each of these fluids in check is essential to keep your car in tip-top shape.

One of these essential fluids is the transmission fluid. While most people know the importance of changing your engine oil, many don’t know exactly what role transmission fluid plays and when to change it. However, it is just as important!

Read on to learn everything about transmission fluid, including what it does, the different types, when to change it, and more.

What Does Transmission Fluid Do?

Transmission fluid lubricates the bearings and metal parts inside a car’s manual gearbox and keeps them from grinding down as they move.

An automatic transmission, not only lubricates the moving parts but also provides hydraulic pressure and friction to make the internal parts work. Transmission fluid in both manual and automatic transmissions also helps to keep the transmission cool.

Shifting gears is a strenuous task for a car, and transmission fluid is what allows a vehicle to shift with ease without wearing down its parts. While manual transmission oil or fluid has existed in some shape or form since the beginning of automobiles, automatic transmission fluid was created in the 1940s and has played an important role in cars ever since.

There are several different types and qualities of transmission fluid, and it’s best to reference your owner’s manual or a trusted auto technician when it comes to choosing the correct fluids for your vehicle.

Transmission Fluid Types

In general, there are two main types of transmission fluid: automatic transmission fluid and manual transmission fluid. Synthetic transmission fluids and specialty fluids are also used and specified in various transmission types including CVT and dual-clutch models.

In order for your car to run properly, it is important to know what type of transmission you have and what specific fluid it requires.

Automatic Transmission Fluid

This type of transmission fluid is designed for vehicles with automatic transmissions. It is also used in some more modern manual transmissions. Automatic transmission fluid meets the needs of automatic transmissions and helps with various functions, including:

  • Gear lubrication
  • Torque converter operation
  • Valve body operation
  • Clutch friction operation
  • Brake band friction
  • Transmission cooling

For more information Check out our Blog: What is Automatic Transmission?

Manual Transmission Fluid

Manual transmission fluid in older vehicles sometimes referred to as manual transmission oil or lubricant, is common on some older manual transmission vehicles.

This heavier fluid from 75W to 140W is never used in vehicles with automatic transmissions. Even if your vehicle is a manual transmission, it does not mean that this type of fluid is used with manual transmission. Most later model vehicles with manual transmissions use an automatic fluid in their manual transmissions.

For more information Check out our Blog: What is Manual transmission?

Synthetic vs. Traditional Transmission Fluid

While traditional transmission fluid is made from crude oil and the conversion of hydrocarbons to the specifications of various vehicles, synthetic transmission fluid is created through various chemical reactions. This type of transmission oil is less likely to break down, oxidize, or thin out at high temperatures.

How do you choose between traditional and synthetic transmission fluid? Unfortunately, this answer is not always black and white. Be sure to check the information provided by the vehicle manufacturer and, if in doubt, contact a transmission specialist.

What Does Transmission Fluid Look Like?

In general, automatic transmission fluids are thinner in consistency and clear with a red hue, although some automatic transmission fluids are now blue/green, purple, or even amber, depending on the manufacturer. This makes it easy to tell apart from engine oil and the other fluids flowing through your car. This also makes it easy to spot a leak.

On the other hand, manual transmission fluid is typically darker in color and thicker inconsistency. It will also have a stronger odor.

How Often Should Transmission Fluid Be Changed?

As mentioned earlier, many people are aware of the importance of changing engine oil, but are not aware of the importance of changing transmission fluid.

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Over time, both the automatic and manual shift fluids will break down and become contaminated with particles and dirt. While the transmission fluid doesn’t need to be changed as often as your engine oil, for example, it’s important to watch it closely and check it regularly.

If your transmission fluid level is low or the fluid begins to break, you will experience a drop in performance when shifting or shifting into gear. This can also increase the risk of damage to internal gears and parts if they grind together due to a lack of lubricant.

Some manufacturers recommend changing the transmission fluid every 30,000-60,000 miles, depending on your driving style and the type of transmission in your car. However, it is important to note that this can vary based on the make and model of your car. Always follow the manufacturer’s recommendations for your specific vehicle.

Towing heavy loads, driving around town, and harsh weather conditions can place greater strain on your transmission and transmission fluid. If you normally ride in these conditions, it is a good idea to check the level and condition of your transmission fluid frequently to avoid problems.

How Do I Know if My Transmission Fluid is Low?

Overheating of the transmission is the most common cause of transmission failure. Overheating of the transmission is typically a result of a lack of fluids or a lack of fluids due to a lack of regular fluid maintenance.

If your transmission system leaks, you will lose transmission fluid and possibly drive low levels. The transmission begins to overheat and slip. While this usually won’t stall the vehicle, the engine will spin faster than normal or it will feel like you have no power.

If your fluid level is low, it can permanently damage your car’s transmission and lead to costly repairs, conversions, or even replacements

Look for any signs of leaks on the ground you are parking on. If your vehicle has an oil dipstick, check the transmission oil level every time you change the oil. If it shows only marginally, you likely have a small leak that turns into a larger one and will cause costly repairs in the future if you don’t fix it early.

Symptoms of Low Transmission Fluid

So how can you tell if your transmission fluid level is low? Here are some key signs to watch out for.

  • Puddles: If you ever notice puddles forming under your car, a transmission fluid leak has likely occurred.
  • Color: Transferring transmission fluid from a light, clear-colored fluid (usually red, but different color in some vehicles) to a darker brown or muddy green color can be a key indicator that it is time to change the fluid.
  • Roaring sounds: If you hear a roar while accelerating or cornering, there may be a problem with your transmission. In addition, a low-fluid transmission can cause whining or buzzing.
  • Chattering: Another common sign of low transmission fluid is a vehicle rattling when it starts. This can feel like you are driving across a rump.
  • Warning light: Many modern cars are equipped with technology to tell you if there is a problem with your transmission. If you ever notice a dashboard light indicating a high transmission temperature, it means your transmission fluid is hotter than it should be. Remember that your indicator light is not always just related to your engine, it can also come on if there is a transmission problem.
  • Difficulties when shifting: Delays in shifting or problems shifting gears such as slipping, sliding, bumps, and noise can be important indicators that there is a problem with your transmission fluid.
  • Transmission slipping or engine revving when going around corners: This is an indicator that you are running low on fluids and not enough to keep the fluid intake in the submerged pan.
  • Smell: A slight burning smell, especially if it has an unusual tart smell to it, can be another sign that there’s an issue with your transmission fluid.

If you have concerns about your transmission fluid, you can easily check its level by pulling the dipstick on most vehicles. The instruction manual tells you where the dipstick is and what level your fluid should be.

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However, some later vehicle models do not have an oil dipstick. So, it is best to see a professional technician who can put the vehicle on an elevator to check the fluid.

What Happens if a Car Runs out of Transmission Fluid?

If your car runs out of transmission fluid completely, it will most likely not be in gear, barely moving, or not shifting at all. This is especially the case if you have a car with an automatic transmission.

Unfortunately, allowing a vehicle to run out of transmission fluid is likely to result in extensive and costly repairs. This is why it is so important to pay attention to the signs listed above! If ever in doubt, check your transmission or take your vehicle to a professional who can check it out for you.

What is a Transmission Flush?

When you are taking care of your transmission, you will often hear the term “transmission flush”.

Essentially, a transmission flush helps ensure that there is practically no old fluid in the transmission, in the torque converter, or in the vehicle’s oil cooler and radiator lines. This is a great way to get rid of any dirt and grime that can get caught in your broadcast.

This maintenance process uses a special machine that removes all of the old, contaminated fluid in the transmission and replaces it with new, clean fluid. Sometimes a cleaning solution is even introduced to improve the cleaning process.

Replacing old transmission fluid with fresh fluid and replacing the filter can help extend the life of your transmission and prevent problems before they happen.

Remember, when caring for your gearbox, always follow your manufacturer’s recommendations. The frequency of fluid changes or transmission flushing depends on your vehicle and the way you use your car or truck.


What is transmission fluid?

Transmission refers simply to the gearbox that uses gear and gear trains to provide speed and torque conversions from a rotating power source (engine) to another device (wheels). Transmission fluid is used to lubricate the components of a car’s transmission for optimum performance.

What are the symptoms of low transmission fluid?

In the meantime, it’s a good idea to familiarize yourself with the tell-tale signs that you may be low on transmission fluid.

  • Noises.
  • Burning Smell.
  • Transmission Leaks.
  • Slipping Gears.
  • Slow Gear Engagement.
  • Vehicle Accelerates Poorly.
  • Check Engine or Transmission Warning Light Is On.

How do you know if you need transmission fluid?

Sudden up and downshifts, spikes in RPMs before shifting strange grinding noises, and erratic shifts are also characteristics of this problem. All of these symptoms indicate you’re low on the transmission fluid and at risk of overheating.

How do I know if I need transmission fluid?

Signs That Your Car Needs a Transmission Flush:

  • Difficulty Shifting Gears – If you ever accelerate and hear your engine rev, but don’t feel your car go any faster, your transmission is likely stuck in gear.
  • Slipping Gears – On the flipside, slipping out of gear is another side effect of having low transmission fluid.

When should transmission fluid be changed?

Automatic: Every 60,000 to 100,000 miles

If you drive manual, most manufacturers will recommend changing your transmission fluid every 30,000 to 60,000 miles. If you have an automatic, you can typically boost that range up to 60,000 to 100,000 miles. There’s no harm in changing your fluid early.

Can I just add transmission fluid?

You can add more by inserting a funnel into the tube the dipstick was withdrawn from and pouring a small amount of automatic transmission fluid into the pipe. Check the level each time you add a little until the level is right between the two lines.

What happens if you drive with low transmission fluid?

Driving your car through a low transmission fluid level is dangerous to you and the vehicle. Failure to top up the fluid is a hazard that might cause extreme damage to the transmission, the engine, and essential components that keep the car running.

Can you lose transmission fluid without a leak?

No. There is no combustion, so it can’t just burn up.

How long can a car run without transmission fluid?

If you check your transmission fluid level and it’s below low, then you’re fine to drive for up to 10 miles as long as you drive slowly.

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How do you know if your transmission fluid is low without a dipstick?

What happens if you don’t change the transmission fluid?

Changing your transmission fluid periodically will increase the lifespan of your transmission. On the other hand, if you never change it, you will have dirty and grimy fluid that will fail to lubricate and disperse heat very well.

How much does transmission fluid cost?

It depends on where you take it. At a mechanics shop or dealer, the price will likely range between $80 to $250. However, if you’re willing and able to do it yourself, it should fall between $50-$100.

Why you should never change transmission fluid?

Changing the transmission fluid on a high-mileage car is risky. Don’t do it unless your transmission is running fine and the fluid is first-rate because it can make transmission failure imminent.

What happens if you mix old transmission fluid with new?

You should not mix the old transmission fluid with a new one. The main reason is it won’t offer you the ideal viscosity. At the same time, the mixing will reduce the performance of the transmission system. So it will cause overall engine performance.

Is It Bad to Start A Car With No Transmission Fluid?

In a car without fluid, there is no hold, the gears cannot spin, and therefore the vehicle will not be able to move. Maintaining your transmission fluid at the right levels and keeping it properly maintained is always a good idea.

How do I add transmission fluid to my car?

Can low transmission fluid cause car not to move?

In an automatic vehicle, the transmission fluid provides a coupling between the engine’s output and the gears in your transmission. If there is no fluid, there is no hold, the gears cannot spin and therefore the car won’t be able to move.

Will the check engine light come on if the transmission fluid is low?

A malfunctioning sensor, low tire pressure, low transmission fluid and so much more will cause the light to come on. But some reasons the check engine light comes on are much more common.

Can you add transmission fluid through the dipstick?

Insert a long funnel into automatic transmission fluid dipstick hole. Carefully add automatic transmission fluid in small increments and recheck the level each time until the fluid level reaches “warm” line. Caution: do not overfill or spill automatic transmission fluid on hot engine parts!

Can you check transmission fluid?

With the engine warmed up, leave the car idling in a park on a level surface. Pull out the dipstick, wipe it clean, replace it slowly, and then pull it back out. Check the fluid level—how high the fluid comes up on the dipstick—against the “full” and “low” or “fill” marks on the dipstick.

Should I change transmission fluid on old car?

And that’s why so many people believe that changing old transmission fluid can cause it to slip. Want to avoid that whole dilemma altogether? Simply change your transmission fluid regularly and you won’t have to worry about it!

Does changing transmission fluid make a difference?

When it starts deteriorating, it will become darker as the fluid gets more burned. This means that the fluid needs a change. Transmission fluid should have a sweet smell, it has this distinct petroleum smell. When it smells bad or smells like it is burned, the fluid is definitely is for a change.

Does changing transmission fluid improve performance?

Changing your transmission fluid regularly, especially when it has turned black, is a great way to improve your fuel economy. Your transmission will run smoother after you change the fluid, which means your engine will run smoother as well.

Can I use oil dipstick to check transmission fluid?

The transmission fluid dipstick is similar to the oil dipstick, while the oil dipstick measures the level of the car’s engine oil, transmission dipsticks measure the level of transmission fluid in your vehicle. Keep in mind many transmission troubles are due to low fluid levels.

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