Too Much Transmission Fluid – Will it damage my Transmission?

transmission fluidSometimes when you are hurry, you may do things like overfilling your transmission by accident.

But will it damage my transmission or can I drive with it? Or should I tap out some of it?

In this article, we will discuss a bit of what happens when you are overfilling your transmission fluid and what will happen if you do so.

The basic working of a transmission

If we talk about the manual transmission, it’s actually simple to understand how it works. A manual transmission resembles an automatic one but with a few differences. The major difference is that manual transmissions are operated with a stick for shifting the gears. There are multiple gears of different sizes inside the transmission where the stick connects. Here, since everything is operated manually, all you need is lubrication to keep the gears inside the transmission cool and run smoothly. Transmission oil is used to achieve that. It is a little different than engine oil but more or less serves the same purpose.

However, the case of an automatic transmission is a little different. These transmissions also contain gears but an additional component known as the torque converter, which makes use of the transmission fluid we are talking about here. Only, here the transmission relies completely on the Trans fluid to operate and without it, the transmission would not at all function. The fluid for automatic transmissions is different from manual transmissions. Here, putting too much transmission fluid, above the full mark even, can cause rather adverse effects.

Will it cause damages to my transmission if it’s overfilled?

transmsision fluidSimilar to the engine itself, transmissions also generate a lot of heat which needs to be cooled down. In manual vehicles, that is achieved by using transmission oil as we talked about. In automatic vehicles, the transmission fluid serves two purposes, one, as a cooling and lubricating agent and two, as the fuel for the transmission to work.

While this fluid is critical for the smooth operation, too much fluid in the transmission can actually ruin the transmission itself. That is because, too much fluid in the transmission will submerge the gears completely in the fluid, which would make the fluid foam up. Because of the foaming and very little room for air, the excessive transmission fluid would overheat the transmission instead of keeping it cool, and without room for air, depressing the clutch would result in fluid trying to ooze out of the transmission, compromising the sealing in the process. This becomes dangerous in automatic vehicles even more.

Consequences of overfilling transmission fluid

As we discussed there are some major causes that could occur if you are overfilling your transmission fluid. Here are some of the most common:

  • Overheated Transmission: Your transmission may overheat if you are overfilling your transmission fluid because of the increased pressure and friction.
  • Transmission fluid leakage: When you add too much fluid, it will cause high pressure inside the transmission, which may cause your transmission to leak fluid.
  • Erratic Shifting: Because of problems with the pressure and the shiftings, you may find problems with your car like erratic shifting if you’ve overfilled it.
  • Foamed fluid: When you have overfilled your transmission fluid you may experience things like foamed transmission fluid inside of the transmission. Check further down for more explanation.
  • Oil starvation: If your transmission fluid is foaming, it may get stuck to the upper part of the transmission and on the gears and everywhere it shouldn’t be inside of the transmission. This can cause the transmission to seize if you are unlucky.
  • Reduced Fluid Lubrication: As we discussed before, the transmission fluid may foam up and this will cause the lubrication to get a lot reduced. This can cause heavy wear on your transmission in the long run.

Since automatic transmission relies on the fluid to work, too much fluid in the transmission will cause erratic gear shifting. That could result in either early shifts or delayed ones along with jerks. The transmission may also make odd noises in the process. Excessive fluid in the transmission may also starve it from the oil itself. The most critical thing about adding too much transmission fluid is that it will cause a big difference in the pressure inside the transmission itself. A certain amount of pressure inside the tranny is maintained along with the fluid which is which there is a limit given on the dip stick. Too much of the fluid will cause an increase in the pressure inside the transmission and you can think of the damage that can cause to it.

So how much fluid should you add?

Transmission fluid shares some similarities with the engine oil. Just how you would get a different reading from the engine oil dip stick when the engine is cold and when it is hot, you would get the same results when checking the transmission fluid level. But there are two situations where the tranny fluid can be checked. It can be checked when the engine is hot as well as when it is cold. Here are a few points to check your transmission fluid:

  • Park your car on a level surface.
  • Pull out the dip stick
  • Wipe the stick with a lint-free clean cloth and reinsert it
  • Pull it out and check the fluid level
  • If the engine is cold, check the cold mark
  • If the engine is warm or still running, check the hot mark
  • If the fluid level too much below marks according to the situations, fill it to complete

Usually, transmission fluids don’t need to be changed that often. Certainly not as much as engine oil. In the case of automatic transmission fluid, the colour of the fluid should be fairly red or pink and the smell shouldn’t be like it’s burnt. Similarly, in manual transmissions, the fluid should not be dark in colour but pink reddish.


So if you have overfilled your transmission, it’s a really good idea to tap out some through the plug or through the dipstick to get the level right. Overfilled transmissions can cause serious damages to your transmission in the long run.

If you have any other questions about transmissions you can search for information on our site or leave your comment down below, I will answer your questions as soon as possible.

1 Star2 Stars3 Stars4 Stars5 Stars (13 votes, average: 5.00 out of 5)

Leave a Comment