10 Signs of Low Transmission Fluid And How To Fix it

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Your transmission fluid is crucial to keeping your engine and transmission running smoothly. Unfortunately, most people pay more attention to their motor oil than their transmission oil. 

As a result, this often results in our transmission fluid getting low without most people noticing. But, don’t worry; I’m here to help. 

In this post, I will go over the causes, symptoms, and solutions to low transmission fluid.

Let’s get started. 

Symptoms of Low Transmission Fluid

1. Check Engine Light Turns On

check engine light

The check engine light does not always come on when you have low transmission fluid. In some cases, it will depend on the type of car that you are driving and how low the transmission fluid is.

If the check engine light does come on, you can confirm the reason by using an OBD reader. The ODB reader will give you exact codes that will help you determine the cause of the check engine light.

One of the most common ODB codes for log transmission fluid is P0686. Most ODB readers will also tell you the reasons for the code if you get a code that is not related to low transmission fluid.

2. Difficulty Shifting Gears

Another common sign that you are running low on transmission fluid is if your car is having trouble shifting gear.

When there is not enough transmission fluid, this will increase the friction inside the transmission. This will make the gears shifting slower and difficult. Difficulty shifting gears is typically easier to notice on manual cars because you will feel it in the stick as you shift.

You can still identify an automatic vehicle that is having trouble shifting. You will typically experience this as you rev your engine and you are nearing the moment of shifting your gears.

As time goes on and you’re transmission fluid becomes thinner, and you lose more fluid, your gears will switch to have a different feeling. As it gets worse, your gear will begin changing faster and start to slip even when you don’t want to shift your gears.

3. Overheating Transmission

overheating signal

Low transmission fluid can cause your transmission to overheat, and this overheating can also cause your engine to overheat.

Transmission oil helps your transmission run smooth and reduces the amount of friction inside the transmission. With low transmission fluid levels, your car will experience more friction, increasing the heat generated inside your transmission.

When your transmission is overheating, this can cause other issues inside your transmissions, such as slippage and a broken transmission solenoid.

With increasing temperatures inside your transmission, this heat will be passed to your engine. The additional heat in the engine can cause your car to overheat and your warning signals to turn on.

4. Transmission Slippage

Transmission slippage occurs when your transmission is not shifting correctly. With low transmission fluid, your gears won’t shift very smoothly. Typically your transmission will struggle to complete a full gear shift.

When there is transmission slippage, your transmission won’t stay in gear. Typically with low transmission fluid, your transmission will “slip” back to the previous gear.

5. Grinding or Whining Noises

Another sign that you have low transmission fluid is a grinding or whining noise. You will likely hear these noises when your engine is about to shift gears or when you are accelerating.

These grinding or whining noises are from the metal-on-metal friction taking place inside the transmission. Without enough transmission fluid, your transmission won’t have enough lubrication to shift gears without friction.

The noise you may hear will vary depending on the car and the amount of transmission oil. For example, you might hear grinding in some vehicles when there is a small amount of transmission fluid. In contrast, other vehicles might not experience any grinding at the same transmission fluid levels.

6. Spongy or Eratic Clutch Pedal

This is a sign that you will only experience if you are driving a manual transmission vehicle. With automatic transmissions, there is no use of a clutch pedal.

With manual transmissions, you will need to use your clutch pedal every time you shift gears. With low transmission fluid, your clutch pedal will become spongy or soft. Likewise, when you push on your clutch pedal, your transmission fluid will become stuck or slow.

In some cases, the pressure on the clutch pedal will become erratic. In some cases, the clutch will be stiff and reliable, while the clutch will be soft and sticky in other cases.

Low transmission fluid will cause low pressure in the line. With low pressure, the clutch pedal will become soft and spongy.

7. Dark or Contaminated Fluid

Dark transmission fluid is another sign that you are running low on fluid. When you have low fluid levels, your transmission fluid will become contaminated much faster than if the fluid was at the ideal levels.

Low transmission fluid levels will shorten the lifespan of the remaining transmission fluid. As a result, the remaining transmission fluid will become thin and worn out, making it less effective and causing more symptoms on this list to emerge.

8. Leaking Transmission Fluid

One of the most common signs that you may have low transmission fluid is leaking or puddles of transmission fluid. Leaking transmission fluid is one of the most common causes of low transmission fluid. Leaking or puddles of transmission fluid are common symptoms of low transmission fluid. 

One of the main reasons for this is that often low transmission fluid will cause leaks if there is not already a leak taking place. For instance, low transmission fluid can cause your transmission to overheat, damaging the solenoid, gaskets, and seals, which can lead to leaking transmission fluid. 

Some of the most common reasons that might cause a leaking transmission include: 

  • Leaking transmission pan. 
  • Broken transmission pan plug. 
  • Broken seals 
  • Leaking torque converter
  • Broken or disconnected transmission lines. 

You want to inspect all of these areas if you suspect a leak in your transmission. The most common area to look for leaking transmission fluid is going to be under your vehicle. Typical leaks tend to accumulate under the vehicle, typically towards the center and where the engine bay meets the windshield. 

Transmission fluid is typically a red or green slick liquid. However, in some cases, when the transmission fluid is running low or deteriorated, the fluid can become almost black or dark red. 

9. Jerk or Lurching Forward

If your car is jerking forward or referred to as lurching forward, this is a sign of low transmission fluid.

When starting your car and accelerating, you will begin to feel a jerk forward and push backward. The jerk is typically rough or hard forwards and a bit slower for the push back.

This typically happens because the transmission is struggling or sputtering. The additional friction and heat inside the transmission will cause the jerking or lurch forward.

If you experience this jerk, you should check your transmission fluid or seek a professional to inspect your vehicle.

10. Erratic Gear Shifting

With low transmission fluid, you will experience erratic gear shifting. Erratic gear shifting will result in your gears shifting too fast or too slow. Typically, when you have the proper amount of transmission fluid, your gears will shift in the same way each time. This will give you some consistency and gives your transmission the chance to work correctly.

When there is a low transmission fluid, the hydraulic pressure is unstable inside your transmission. This unstable hydraulic pressure will cause your gears to shift erratically.

You can test the consistency of your gear by going through each gear. You should feel and experience the same speed and smoothness each time your shift. You can test this with both automatic and manual transmissions.

If you experience a fast or slow gear shift at any point, you need to check your transmission fluid or take your vehicle to a professional.

What Causes Low Transmission Fluid?

1. Not Adding Enough Transmission Fluid

One of the main reasons for low transmission fluid is not adding enough transmission fluid, to begin with. This can often happen when people try to refill their transmission fluid on their own. This can sometimes cause people not to add enough transmission fluid.

Another thing that can cause low transmission fluid is just topping off your transmission fluid. Again, this can reduce the quality of your transmission fluid and cause you not to add enough transmission fluid.

You should always check your transmission fluid levels after you add transmission fluid. Your dipstick should show the transmission fluid up to the full line. Typically you want to add in about half-a-quart of fluid at a time. This will make it easier to make sure you add the perfect amount of transmission fluid.

Different cars require different amounts of transmission fluid. For example, the Honda Accord only takes about 3 quarts of transmission fluid, while the Nissan Altima takes around 7 quarts of transmission fluid.

When adding transmission you want to check your owners manual or do a quick google search to determine the appropriate amount of transmission fluid in ou

2. Leaking Transmission

Another common reason you might be experiencing low transmission fluid is a leak in your transmission. There are many gaskets, valves, and pans that can cause your transmission fluid to leak out. 

Some of the most common reasons that might cause a leaking transmission include: 

  • Leaking transmission pan. 
  • Broken transmission pan plug. 
  • Broken seals 
  • Leaking torque converter
  • Broken or disconnected transmission lines. 

You want to inspect all of these areas if you suspect a leak in your transmission. The most common area to look for leaking transmission fluid is going to be under your vehicle. Typical leaks tend to accumulate under the vehicle, typically towards the center and where the engine bay meets the windshield. 

Transmission fluid is typically a red or green slick liquid. However, in some cases, when the transmission fluid is running low or deteriorated, the fluid can become almost black or dark red. 

3. Hole In The Transmission Line

One of the most common causes of low transmission fluid is a hole in your transmission line. The transmission line connects your transmission to your radiator. If there is a hole in these lines, your transmission fluid will leak out, causing your transmission fluid to run low.

Transmission lines can be made of different materials such as aluminum, rubber, brass, or steel. Certain lines are more susceptible to damage than other materials. For example, if your car has rubber or aluminum transmission lines, they are more likely to experience a hole in your transmission line.

Remember that only automatic vehicles have transmission lines. Manual transmissions don’t have any transmission lines, so this may not be the reason.

4. Solenoid Malfunctions

One reason your transmission may be running with low transmission fluid is that your solenoid is malfunctioning. 

The solenoid acts as a valve that controls the amount of transmission fluid released into your transmission. 

When the solenoid is malfunctioning, there may be sufficient transmission fluid in your system, but not enough is reaching the crucial parts of your transmission to allow it to function correctly. 

The transmission solenoid can fail due to multiple reasons. Some of the most common reasons that the transmission solenoid may malfunction include: 

  • Electrical malfunctions 
  • Dirty or contaminated fluid causing the solenoid to get stuck closed. 
  • Overheating transmission

How To Check Your Transmission Fluid?

Checking your transmission fluid is not difficult. You can follow the simple steps below to check your transmission fluid.

There is two methods to check your transmission fluid: cold and hot check.

The cold check includes checking your transmission fluid when it’s cold, or you haven’t been driving.

The hot check involves checking the transmission fluid after driving or after letting it run so that the fluid is hot.

I typically recommend checking your transmission fluid when it’s hot because this produced a more accurate measure than the cold check.

1. Locate The Dipstick

The first thing you need to do is locate your transmission dipstick. The transmission dipstick is located under the hood near the engine compartment.

It’s important to distinguish between the engine and transmission dipstick. This is important because you don’t want to add transmission oil to your engine.

You can check your owner’s manual or do a google search for your specific car to determine where your transmission fluid dipstick is located.

2. Park on A Flat Surface

You want to park your car on a flat-level surface to ensure that you get a proper reading. An unleveled surface will give you an inaccurate reading.

3. Check your transmission after driving

The hot check produces the most accurate results. This means you should check your transmission fluid after driving for around 5-10 miles.

An ideal hot check involves checking your transmission fluid when the fluid is between 150 degrees Fahrenheit and 200 degrees Fahrenheit.

4. Remove Your Dipstick and Clean it

After reaching the ideal temperature, you want to remove your dipstick and clean it off with a rag or paper towel. This step is designed to create a baseline for your transmission fluid.

5. Insert your Dipstick

read_dipstick_low

Once you’ve cleaned your dipstick, re-insert the dipstick to get your reading. After cleaning, this should give you an accurate reading.

With a hot check, your fluid levels should fall in the “hot” range of the dipstick. If there is not a hot range, it should fall in the upper end of the measurement lines on your dipstick.

If your dipstick has a “hot” measurement box, your transmission fluid should fall somewhere in this box.

If your dipstick uses the “Add/Empty” / “Full/Do Not Add” measurement style, you want your transmission fluid to be above the “Add” lines and “Do not add” lines.

6. Check your transmission fluid 2-3 times.

You should clean off your dipstick and check your transmission fluid at least 2-3 times. You want to make sure that you get consistent results or very similar results each time.

If you are getting drastically different readings each time, this can signify a clog or other issue with your transmission. Have a professional inspect your transmission to determine the reasons behind the inconsistent readings.

Solutions To Low Transmission Fluid

Fixing your low transmission fluid is not as hard as it sounds. If you have low transmission fluid, you need to add fluid to ensure you have enough to operate properly.

1. Add Transmission Fluid

If you have low transmission fluid, the first thing you want to do is to check your levels and then add more fluid. 

  1. Before adding transmission fluid, you want to check your owner’s manual to make sure you use the correct transmission fluid. 
  2. Remove your dipstick and insert a funnel. 
  3. Add transmission fluid 1/4 quart at a time. This will prevent you from adding too much or too little transmission fluid. 
  4. Remember to pour the transmission fluid slowly and allow your transmission to eat the fluid. 
  5. After adding your transmission fluid, check your levels and determine if you need more. 

2. Inspect For Leaks

You can add as much transmission fluid as you want, but if there is a leak, you will quickly have low transmission fluids again.

After adding transmission fluid, you want to check for any leaks. You should check immediately after adding the transmission oil, but you should also check after you drive and before you drive for the next several days.

In some cases, fluid won’t leak until after you drive or after the car cools down.

You want to look for a red or green slick liquid under the front of your car. You should also look for any signs of leaks around your transmission or inside your hood.

3. Take Your Car To a Professional Mechanic

If you are not comfortable changing or checking your transmission fluid you can take your car to a professional mechanic.

Changing transmission oil is a routine process that any professional mechanic can complete relatively quickly.

You should also take your car to a professional if you do see signs of a leak. Identifying the source of a leak is not easy and typically requires professional assistance.

Can You Drive On Low Transmission Fluid?

Yes, you can drive on low transmission fluid, but it’s not a good idea. You should only drive on low transmission fluid to get transmission fluid or reach a mechanic to change your transmission fluid.

Driving on low transmission fluid can cause other damage to your engine and transmission. Not only can low transmission fluid lead to more damages, but it can also result in terrible driving conditions such as slippage, difficulty shifting, and an overheating engine and transmission.

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