We are sure we all have heard the ‘too much of a good thing’ warning and nothing can be more true when it comes to your ATF or Automatic Transmission Fluid. Here we will be talking about what happens if you overfill transmission fluid, the signs of overfilled transmission, and most important of all, how to go about correcting this when it happens.

When your transmission fluid runs low, it can cause noise and grinding sounds coming from the transmission. The problem is, when it gets to the point that you can hear something, there could be enough damage to cost you a pretty penny. The same goes for too much transmission fluid, as an overfilled transmission fluid can also cause many mechanical problems down the line. When it comes to your ATF, it is best to always go according to your vehicle’s specification which is in the sweet spot, not too much and not too little either.

How does a transmission work?

A transmission works as it is named, it transmits the engine power to the wheels thus enabling the vehicle to move. Now there is manual transmission and then there is automatic transmission. A manual transmission is a bit harder to master than an automatic transmission, as it involves quite a handful of extra steps to get the car moving.

Here, we will be focusing more on automatic transmission, as this is the type of transmission that requires the automatic transmission fluid or ATF. With an automatic transmission, fluid effects and fluid problems become a factor in making sure your car is in top running condition.

The Automatic transmission

A vehicle equipped with automatic transmission is so much easier to drive and operate than a manual transmission as the car shifts the gears for you. All the driver needs to do is to steer the car and step on the accelerator and the brakes. In an automatic transmission equipped car, the drive system determines when to downshift or engage higher gears depending on the car’s speed. Instead of using clutches and pressure plates, it uses a torque converter to shift gears at different speeds.

Automatic transmission uses hydraulic pressure to change gears according to the car’s need. It does this by combining a fluid coupling and uses hydraulics or pressurized fluid to shift up and down the gears. This allows the car to maintain engine idle without stalling even at a complete stop. The hydraulic system is why part of the symptoms of too much transmission fluid is slippage as it cannot maintain the proper pressure when there is too much or too low fluid.

CVT Transmission

If automatic transmission replaced manual transmission and made driving a car simpler, CVT or continuously variable transmission made automatic transmission more fuel efficient. Not only that but CVT also offered a smoother driving experience overall. Normal, older automatic engine transmission has a fixed set of gears that the engine can use accordingly.

The CVT however, uses a pulley system and has an infinite number of gears to utilize. This makes the CVT equipped vehicle smoother to drive because it technically doesn’t change gears at all, but rather adjusts the width of the pulleys. It is important to note though, that whether you use a regular automatic or a CVT, the concept of transmission fluid too high is still very much in effect.

What happens if you add too much transmission fluid?

As promised, we will be talking about whether is it bad to have too much transmission fluid or if overfilling automatic transmission fluid is okay to the point of being negligible. To make sure you do not miss any of the symptoms and remove the guesswork, below is a list of what happens when the transmission fluid overfilled.

✔ Problems in Shifting

When you have your transmission overfilled by 1 quart, it would cause abnormal reactions to your transmission. So, if you are asking can too much transmission fluid cause slipping, it definitely will. Not only will you experience slippage, but high transmission fluid can also cause foaming, and in turn will cause higher transmission temperatures. This brings about a myriad of problems, from not shifting smoothly, slippage, and insufficient gear or belt lubrication.

✔ “Overfilled” Dipstick

While at first thought this may not seem to be a big problem, incorrect fluid readings can lead to bigger troubles. The dipstick is there so that you can take a look at how much transmission fluid you have. Overfilling the transmission fluid level will cause the dipstick to give inaccurate reading, telling you that you have a lower level when in fact you are overfilling the shafts. For the best and most accurate results, it is recommended to check the dipstick when the car is on a level surface and when the engine is cold. Another problem that will cause problems with the dipstick reading is that fluid can accumulate inside the walls of the dipstick port, causing it to smear the stick itself, giving further inaccurate reading.

✔ Leaking Transmission Fluid

One thing that will be more than an inconvenience would be the buildup of too much pressure inside the transmission chamber. This can lead to seals blowing up and losing their integrity. When this happens, you may dry your transmission of essential lubrication and cause some real damage as you drive.

✔ Erratic shifting

With more than the recommended amount of fluid in your transmission, the gears as well as the pulleys will be submerged in the fluid, causing erratic pressure build-up. When this happens, all sorts of problems will be experienced when you shift. Too much transmission fluid can cause gears to slip and do some damage to other internal parts. If left unchecked, this damage will cost hundreds and even thousands of your hard earned money to fix.

✔ Oil starvation

When a transmission system experiences being filled up with too much ATF, it can have a negative effect on the fluid’s viscosity, affecting its ability to reduce friction as well as its ability to properly engage the gears appropriately. This is especially true when the transmission fluid starts foaming. If you listen closely or upon bringing your car to the mechanic, they will tell you and let you listen to grinding noises from the transmission.

✔ Lack of lubrication

When the vehicle’s ATF is filled above the recommended amount it will most probably lead to foaming. Foaming occurs when there is air and oil mixture inside, this will cause improper lubrication and friction will occur causing heat. It is not just heat, but when there is little to no lubrication, abnormally fast wear and tear will occur. This can lead to expensive repairs in the long run when left unattended.

✔ Transmission fluid leakage

Filling the transmission fluid above the limit will cause problems with pressure. Remember these fluids are maintained in the recommended level for a reason and are an exact science. When there is too much pressure build-up the tolerances for the seals as well as o rings will be compromised. When these seals break and give up, your ATF will come rushing out and you have got a leakage. This is very concerning as it’s never good to run out of stuff that lubricates metal parts.

✔ Transmission overheating

Overfilling will also cause the internals of your transmission to fill up with fluid, driving the air that partially cools the parts. This can lead to overheating and in any part of the engine that is never good. Overfilling will almost make the fluid produce foam, and this will negate any lubrication properties of the fluid. With the lubrication compromised, metal parts will grind against each other creating friction, eventually breaking down from extreme heat.

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We realize we cannot pack all relevant information here, so we gathered up what people are talking about when it comes to overfilled transmission fluids. Just to make sure we are delivering all the needed information, below are some of the most asked questions regarding automatic transmission fluid.

Frequently Asked Questions (FAQs):

How Do I Know When To Change My Transmission Fluid?

Not all engines are equal and that goes the same way for their ATF requirements and with this, the first thing you need to do is get the information from your owners manual. This will give you the information you need for the exact required liters for your particular vehicle. In the absence of the owner’s manual, check the dipstick as it will usually have markers for maximum and minimum fluid amount.

Also, you can smell and visually inspect the condition of the transmission fluid. If the fluid appears darker and smells burnt, that is usually a good indication that it needs a change. Combine these with good old common sense, such as how many miles has the car run and what kind of loads are you subjecting the car to. Hauling heavier loads translates to changing the fluids more often and at closer intervals.

How Much Fluid Do I Add?

This usually applies to top ups on your existing automatic transmission fluid. First up there is a need to get an accurate reading from your reservoir and dipstick. Make sure that you park your car on level ground and leave it until the engine is cold to the touch (might take a few hours).

This is to ensure that you get a correct and accurate reading as to the fluid level in the compartment. This is by far the most accurate way of knowing how much fluid to add in an ATF top-up. This is also a good time to inspect the color and smell of your transmission fluid. If the ATF color is reddish or pinkish it’s still good, but if the color is dark and smells burnt, maybe a change is in order instead of just adding fluid.

How do you remove excess transmission fluid?

Removing the overfill can be a bit tricky, because you need a certain equipment to siphon off excess fluid called the filler tube or a liquid transfer pump. The concept is the same as water changers but this time fluid only goes out, thus removing whatever you need to be gone. This is a relatively simple operation but if you are a novice it can get messy and take up some time.

One of the easiest and mess-free ways is to get your car to a trusted mechanic, and the job can be done usually in under an hour.

Can too much transmission fluid cause the transmission to slip?

Yes, unfortunately slippage is among the numerous transmission problems that can be caused by having too much fluid. Having too much transmission fluid can throw around wrong pressure readings and cause slippage in the gears or pulleys.

Primary reason is that when the fluid is too much it can cause the fluid to mix with air inside the transmission chamber, leading the fluid to form foam. Foam can cause overheating while compromising its ability to lubricate metal parts.

Why does my car jerk when shifting gears with automatic transmission?

This ‘jerking’ movement is what you feel when the transmission slips its gears. This is a common indication of incorrect fluid levels inside your transmission which means it could either be too low or too high.

Also it is not confined to jerks, but one can also experience shuddering, shaking, grinding noises, and hard shifting. All of which point to lack of or too much fluid in the transmission.

Will an overfilled transmission leak?

Yes it will, because if the overpressure does not pop the seals, the overheating transmission will. It is a waterfall effect if left unattended for too long. The damage can transfer from the transmission gears to other components. FOam in the overfilled fluid can break the integrity of the seals causing automatic transmission fluid to leak.

Remember that ATF is already being pressurized to move the gears into their corresponding places adding too much can cause overpressure.

What do I do if I put too much transmission fluid in my car?

When you find out that you have too much transmission fluid, ensure that you bring it down to recommended levels as fast as possible to avoid long-term damage. There are several ways to know the level of your ATF and getting rid of the excess can be done DIY style or a quick trip to the auto shop.

Considering the damage it can do, spending an hour or two correcting the fluid level is a small price to pay.

Can too much transmission cause limp mode?

The CEL (Check Engine Light) for transmission will come on when it detects any problem with the transmission. When this happens, the car can either bypass some systems and limit power to the engine to prevent damage.

The ECU (Engine Control Unit) or the car’s computer will only allow the car to travel under greatly reduced power, thus the term ‘Limp’ mode. This is designed to get you to a safer location such as a garage to make repairs.


All fluids in the car’s engine adheres to specific characteristics including how much they need to contain and is an exact science. This means you cannot put too much or too little. Always follow the manufacturer’s recommendation and you will suffer less maintenance headaches. Make it a habit to always check levels and you are well on your way to enjoying a trouble-free ride for a long time.

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