The transmission fluid is a vital part of your car or truck that keeps various moving/hydraulic parts in the transmission, such as gears, bearings, shafts, and other metal parts, well-lubricated.
It is crucial to protect the gears and clutches by ensuring the right level of transmission fluid to maintain the optimal performance of your vehicle.
Overfilling the transmission can cause excessive friction and wear, leading to reduced performance and overheating of the engine.
A periodic refilling of the transmission fluid to the appropriate level is essential for the smooth operation of your car’s transmission system. While it’s easy to fill the fluid, removing the excess isn’t that easy and has to be done properly.
Overfilling can result in major complications/various problems affecting the overall performance and longevity of your vehicle, even though an influx of fluid is not necessarily a sign of a problem with the car.
What Is Transmission Fluid?
Transmission fluid is a specialized lubricant used in automatic and manual transmissions of vehicles. It serves multiple purposes within the transmission system.
Primarily, transmission fluid acts as a lubricant, reducing friction between the moving components of the transmission.
This helps to prevent wear and tear on the gears, bearings, and other internal parts, ensuring smooth operation and longevity of the transmission.
In addition to lubrication, transmission fluid also plays a crucial role in cooling the transmission.
The fluid absorbs heat generated by friction and heat dissipation within the transmission, helping to maintain optimal operating temperatures.
Furthermore, transmission fluid acts as a hydraulic fluid, facilitating the transfer of power within the transmission system.
It enables the smooth shifting of gears in automatic transmissions and provides the necessary pressure for engaging the clutch in manual transmissions.
What Does Transmission Fluid Do?
Transmission fluid plays multiple roles in an automatic transmission. First and foremost it lubricates all the moving parts to prevent metal-on-metal contact from rapidly grinding away on the sophisticated gears inside the housing.
Transmission fluid also helps transfer pressure through the valve body, which acts as the brain of the transmission, helping to shift gears.
It does this by activating and deactivating solenoids which divert pressure to activate the clutch packs and bands that engage and/or disengage gears.
Transmission fluid also plays a role in how the transmission cools itself. It moves through the pressurized system to fluid lines that carry it out to the lower portion of the radiator or a special transmission radiator.
The fluid then releases some of its heat energy and returns back to the transmission to help keep it operating within a safe temperature range.
When the transmission fluid is too low, these systems are impeded. Gears can grind, the valve body doesn’t have sufficient pressure to change gears via the solenoid action, and heat energy doesn’t dissipate efficiently.
Though too much transmission fluid can also mimic some of these same problems.
Causes Of Overfilled Transmission Fluid
Sometimes, incorrect maintenance can lead to too much transmission fluid. This can happen if the person adding fluid does not check the current level. Too much fluid can cause many problems.
The transmission may not work properly. Fluid pressure can increase inside the system, causing leaks. These leaks can damage other parts of the vehicle.
Thermal expansion happens when the transmission fluid heats up. Hot fluid expands and takes up more space.
If the transmission is already full, this can cause overflow. Overflowing fluid can lead to many issues. The fluid may foam, causing shifting problems. It can also put extra stress on the transmission system.
#1. Immediate Effects On Your Vehicle.
Too much transmission fluid can cause increased pressure inside the transmission. This pressure can damage seals and gaskets.
Leaks may occur. The transmission may overheat. Overheating can lead to serious issues. Your car may not shift smoothly. It can be hard to control.
Excess fluid can cause the transmission fluid to foam. Foam reduces the fluid’s ability to lubricate. Poor lubrication can cause wear and tear. Parts may break down faster.
Your car may jerk during shifts. Foam can also lead to overheating. Overheating is dangerous for the transmission.
#2. Long-term Damage Risks.
Too much transmission fluid can cause foaming. Foaming makes the fluid less effective. This can lead to transmission slippage.
Slippage means gears do not shift smoothly. The car may feel jerky. Over time, this can wear out the transmission system.
Excess fluid can create pressure inside the transmission. High pressure can damage seals. Damaged seals may cause leaks. Leaks lead to low fluid levels. Low fluid levels harm the transmission. This can result in costly repairs.
What are the Consequences of Overfilling Transmission Fluid?
Overfilling the transmission fluid can lead to various negative outcomes. Here are the potential consequences associated with overfilling:
#1. Transmission Failure.
Overfilling the transmission fluid can have severe consequences, such as transmission failure.
When the fluid level is excessively high, it exerts excessive pressure on the seals and gaskets within the transmission—the increased pressure cause these crucial components to develop leaks or even break altogether.
As a result, the transmission loses hydraulic power, leading to transmission failure.
#2. Increased Wear on Transmission Components.
Overfilling the transmission fluid places undue stress on the transmission gears and components. The excess fluid creates additional resistance and makes it more difficult for the gears to engage properly.
This added strain can accelerate wear and tear on the gears, causing premature damage such as stripped teeth or even gear breakage.
#3. Inadequate Lubrication and Foaming.
Excessive transmission fluid can lead to inadequate lubrication and the occurrence of foaming.
When the fluid level is too high, the moving gears and components may not receive sufficient lubrication. Inadequate lubrication increases friction and heat generation, which can result in damage to the gears and other transmission components over time.
Additionally, the excess fluid can foam, further compromising the lubrication process.
Foam does not provide the same level of protection and smooth operation as properly lubricated fluid, increasing the risk of wear, overheating, and potential failure of the transmission system.
#4. Excessive Pressure Buildup.
Overfilling the transmission fluid leads to the buildup of excessive pressure within the transmission system. The excess fluid creates a higher-than-normal hydraulic pressure, which can strain the seals and gaskets.
The increased pressure can cause these components to fail, resulting in fluid leaks and potential damage to other parts of the transmission.
What happens if you add too much transmission fluid?
One should know what are the symptoms of too much transmission fluid before driving the vehicle/car.
Here are some of the common signs and symptoms of excessive transmission fluid and how they impact a car’s performance and affect the driving experience.
#1. High Fluid Level on Transmission Dipstick.
You can determine the higher fluid levels by using a dipstick (a type of testing stick). It is used to check the fluid level in the gearbox.
Measure the transmission fluid level properly on the dipstick by running the motor/engine for 10 minutes to get the even consistency of the fluid, yet ensure the car’s temperature isn’t high, as the fluid swells a bit at high temperatures.
Then use a dipstick tester even if you are not using or running the car to estimate the transmission fluid level.
#2. Difficulty Shifting/Changing Gears.
Since transmission fluid lubricates the moving parts for easy moving, the volume of the fluid should be approximate (not too much or too little) to prevent some space difficulties, including gear shifting issues in both automatic and manual transmission vehicles.
Manual gearshift requires much power (extra effort) to move compared to the automatic gearshift.
If you notice that gear shifting is more difficult than usual, it’s important to address the issue promptly to prevent any further damage to the parts involved (degrade quickly).
#3. Engine Overheating.
Do you know that the excessive volume of transmission fluid in the vehicle might result in engine overheating, instead of protecting the gearbox and engine from excessive heat?
This is due to the excessive friction and heat buildup (reduces cooling efficiency) caused by the excess fluid in the transmission.
Overheating of the motor and other internal parts can lead to premature failure (wear & tear) and expensive repairs. So, it’s important to monitor fluid levels and address any issues promptly.
#4. Leaking Fluid.
An eventual burst in the gaskets occurs due to the rise of fluid pressure in the gearbox/transmission seals or vents, resulting in the leakage of red fluid from the car through its break or fracture holes.
This can damage other parts and components (including sensors, or electrical connections), affecting the overall performance of the transmission system.
It is expensive to repair a leaky seal, as it involves fluid draining the fluid and manual replacement of the gasket.
#5. Foaming or Bubbling Fluid.
Too much transmission can cause aeration or foaming, which reduces the fluid’s ability to lubricate and cool the transmission components.
This leads to a decrease in viscosity, noticeable bubbles on the dipstick, inside the fluid reservoir, and can compromise the ability to maintain proper hydraulic pressure, causing erratic shifting and slipping gears.
#6. Strange/Odd Noises.
It is common for vehicles to make sounds when their parts are not functioning correctly. If you hear whirling, moaning, churning, humming, or buzzing sounds while accelerating or decelerating, it might be a sign of an overfilled transmission in your gearbox.
For example, changing gears can produce a clucking noise, while a gurgling or bubbling noise may occur when the car is idle due to an overfilled transmission fluid. However, an overloaded transmission does not usually make piercing sounds.
Therefore, it is essential to be observant and cautious and take necessary action if you notice any strange noises.
#7. Slipping Transmission.
Excess fluid in the gearbox can create pressure on the internal engine components, causing the gearbox to jolt or slip out of gear (or experience delayed engagement).
Automatic cars may experience clunkiness and slight acceleration loss, while cars with manual gearboxes require manually shifting the gearbox back into gear.
Additionally, a grinding or high-pitched whining sound may occur when the gearbox slips while driving.
#8. Component Pitting/Chipping.
If you leave the excess transmission fluid in the gearbox for an extended period, it might result in chipping off the parts.
It eventually damages the vital mechanical parts (ball bearings or cogs) in the gearbox. This part-wearing will collapse the gearbox, leaving you to either replace or repair it.
#9. Delayed Engagement & Difficulty Reading Fluid Levels.
The overfilled transmission might take a bit longer to engage in gear while shifting from Park to Drive (or) Reverse.
This delay is a sign of hydraulic pressure issues due to excessive fluid. While checking the transmission fluid level on the dipstick, an overfilled transmission might show inaccurate or inconsistent readings. Thus, it is challenging to determine the actual fluid level.
How Does a Transmission End Up with Too Much Fluid?
The most common reason why transmission fluid ends up getting overfilled is due to an excess abundance of caution by the driver. They mistakenly think that they need to err on the side of caution by adding more transmission fluid.
#1. Mistaking for Low Transmission Fluid.
The car’s owner might hear a strange noise that they mistakenly think is a sign of low transmission fluid.
Since a lot of modern cars have sealed transmissions without a dipstick, they err on the side of caution and pour some through the transmission fluid add port at the top of the engine.
They keep driving, and they hear strange whirring noises or notice that the gears aren’t shifting normally.
Jumping to the conclusion that they still didn’t have enough, or that there might be some unseen leak, they pour a bunch more in. Yet still, the problems persist, and likely even get worse.
#2. Error in a DIY Transmission Fluid Change.
The next most likely reason why a transmission might be overfilled is an after-effect of a DIY transmission fluid change.
When you drain a transmission to change the fluid, rather than performing a flush and fill, there’s naturally going to be some transmission fluid still left in the system. In some cases, 20 to 40% of the old transmission fluid remains.
If you pour in the full volume of fresh new fluid, the combined volume with the old fluid can cause it to be grossly overfilled.
While this can sometimes happen at rapid-change auto shops, most of the time, it’s a home mechanic who overfills it on accident.
How To Fix An Overfill transmission fluid
If you have overfilled your transmission fluid, there are steps you can take to rectify the situation. Here’s a guide on how to fix an overfilled transmission:
- Safety First: Ensure that the engine is turned off and the vehicle is parked on a level surface. Engage the parking brake to prevent any unintended movement.
- Locate the Transmission Fluid Drain Plug: Consult your vehicle’s manual to find the location of the transmission fluid drain plug. It is typically located on the transmission pan, which is located underneath the transmission. Some vehicles may require the removal of a protective cover to access the drain plug.
- Prepare Drain Pan: Place a suitable drain pan beneath the drain plug to catch the excess fluid that will be drained.
- Loosen the Drain Plug: Use a wrench or socket to loosen the drain plug. Slowly loosen it until fluid begins to trickle out. Take caution, as the fluid may still be hot.
- Drain Excess Fluid: Allow the excess fluid to drain into the pan until it reaches the proper fluid level on the dipstick. It is advisable to drain the fluid in small increments, periodically checking the fluid level to avoid draining too much.
- Tighten the Drain Plug: Once the excess fluid has been drained and the fluid level is within the recommended range, tighten the drain plug securely.
- Check Fluid Level: Start the engine and allow it to reach operating temperature. With the engine running, check the transmission fluid level using the dipstick. Add or remove fluid as necessary to ensure it falls within the recommended range. Be cautious not to overfill or underfill the transmission.
How Much Transmission Fluid Does a Car Hold?
It really depends on the type of vehicle you drive. Most cars take about 4 to 10 quarts of transmission fluid, but some passenger vehicles can take as much as 17 quarts!
Because of this it’s important that you know where to look to figure out how much transmission fluid your vehicle takes.
The first place you can look is your owner’s manual. This will tell you exactly how much oil your transmission takes, and it’ll tell you what kind of fluid to use.
If you don’t have your owner’s manual anymore, you can reach out to a local dealership or use Google to track it down. Just be careful when using Google that you’re only getting information from a reliable source.
What is The Required Transmission Fluid to Fill in The Vehicle?
The volume of transmission fluid varies from one automobile model to another (irrespective of vehicles of the same group) depending on the vehicle’s fuel types, gearbox configuration, engine size, and limited-slip differential.
Vehicles operating on modern diesel fuel systems and automated transmissions use much more transmission fluid than their previous versions, including manual).
Whereas, the consumption of transmission fluid is much less than semi-automatic and automatic versions.
Here is a handy table that provides an outline of the required transmission fluid for certain vehicles.
| Types of Cars | Required Transmission Fluid |
| Sedans, City Cars, and Family Cars | 1.7 to 9.7 liters |
| Roadsters and Convertibles | 1.9 to 10 liters |
| Muscle Cars & Coupes | 3.8 to 12.8 liters |
| Station Wagons, Tourings, and Estate Cars | 0.9 to 9 liters |
| Electric Cars & Eco Cars | 1.4 to 3.8 liters |
| Microcars | 2.4 to 6 liters |
| Liftbacks, and Hatchbacks | 1.8 to 8.6 liters |
| Mini-vans and CUVs | 1.9 to 9.2 liters |
| Limousines | 9 to 11.3 liters |
| Pickups and Commercial Cars | 2 to 11.3 liters |
| Supercars, Sports Cars, & Grand Tourers | 1.6 to 11.3 liters |
| SUVs, and Subcompact Cars | 3.3 to 16.2 liters |
How to Check & Drain Transmission Fluid a Step-by-Step Guide
If your car has a dipstick for the transmission fluid then checking it is easy. Unfortunately, a lot of newer cars these days have “Sealed Transmission” without a dipstick.
This makes them increasingly prone to accidentally overfilling the transmission fluid or the fluid is very low, as the driver feels like they have to guess.
Though there is a way to check the fluid levels in a sealed transmission. It just takes a little bit of extra time, effort, basic tools, and an oil drain pan.
- Find the inspection plug and fill plug. The inspection plug looks like a bolt on the side of the transmission housing and the fill plug usually has a black plastic cap on the top of the transmission accessible under the hood.
- Take the car for a short drive to get the engine and transmission fluid warmed up. This will cause it to expand slightly to give you the most accurate reading possible. Just bear in mind that you want it slightly “Warm” not hot.
- Set the parking brake, and you might need to jack the car up and block it off to safely work on the inspection plug from below.
- Use a wrench to loosen the inspection plug on the side of the transmission. Place a drip pan under the plug and catch the excess transmission fluid that comes out.
- Wait at least 15 minutes to let all the excess transmission fluid drain out of the case. Periodically check the transmission fluid to see if it’s dark, foamy, or has metallic flakes. If it does, you might need a complete transmission flush & fill and/or a transmission tune-up.
- Reinsert the transmission inspection bolt.
- Let the car sit overnight or at least 8 hours to try to let any bubbles in the transmission fluid settle out.
- Check the fluid again to see if the bubbles have settled out of the fluid. If they have, you take the car for a test drive to see if the symptoms of overfilled transmission fluid are gone.
Prevention: Keeping Your Transmission Happy
- Stick to manufacturer specs: Always follow your service manual’s fill procedure.
- Use a pump or precise suction tool: Pouring in fluid from a jug invites over-pouring.
- Double-check with the dipstick: Before and after a fluid change, measure twice.
- Schedule regular fluid and filter changes: Fresh ATF cuts friction, prevents foaming, and prolongs seal life.
A little extra care under the hood prevents big headaches down the road.
FAQs.
Q: How do you remove excess transmission fluid?
The simplest means of removing excess transmission fluid involves taking your car to a service garage or draining the fluid yourself. You can drain the fluid by removing the crankcase plug or applying a filler tuber.
If you choose to go with filler tuber, you’ll need to invest your time in it. You will have to hold the filler tube until the fluid reaches the cap, then pull it out and drain it into a catch pan.
Q: Can too much transmission fluid cause the transmission to slip?
Excess transmission fluid can cause several adverse effects on the transmission. If the fluid stays above the recommended level, it can cause it to start mixing with air. This can lead to gear slippage, hard shifting, and other transmission shifting issues.
Q: Will an overfilled transmission leak?
Overfilled transmission fluid might not damage your transmission seals, but it will cause them to leak. The transmission is designed so that pressure won’t leak in unpressurized areas. If a high pressure occurs due to excess fluid, it will leak through the seals.
Q: Why does my car jerk when shifting gears with automatic transmission?
Several factors could cause your automatic transmission to jerk when shifting gears. However, here are common causes that you should watch out for; if you feel jerky, shaky, or hard shifting, it could mean you need to change your transmission fluid or the fluid level is low.
Q: What do I do if I put too much transmission fluid in my car?
Once you notice you have too much transmission fluid in your car, you need to act fast to avoid letting it cause severe damage to the system components.
You can either take your vehicle to a service garage or reduce the fluid yourself. You also have to keep the fluid at the recommended level.
Q: Can too much transmission cause limp mode?
When internal transmission or engine sensors detect issues with the transmission, it will place the car in limp mode.
So, you can drive safely to a dealership or mechanic garage for a repair. And if you continue driving your state in this state, it will cause catastrophic damages, and you don’t want that to happen.
Final words
The proper functionality of every transmission relies on the fluid, as it is the lifeblood of the transmission. Adding too little fluid to your transmission will expose it to premature wear and tear.
On the other hand, adding too much transmission fluid can cause severe system damage. If this happens, it will lead to an expensive repair. Once you notice any of the above signs or effects, fix it immediately before it escalates.