What Will Happen If You Overfill An Automatic Transmission?

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As soon as you notice that something is out of the ordinary while using your car, it’s time to think about the problem and fix it. For example, what happens if you overfill an automatic transmission?

What Will Happen If You Overfill An Automatic Transmission
What Will Happen If You Overfill An Automatic Transmission?

When you overfill the automatic transmission, excessive fluid could make the automatic transmission foamy, causing erratic shifting, loss of internal lubrication, and possibly transmission damage. And carefully follow the directions in your owner’s guide when checking and adding fluids.

In detail, let’s see what happens if you overfill an automatic transmission and some ways to check the oil in an automatic transmission.

Adding gear oil to a manual transmission

For filling the automatic transmission, it is necessary to determine the filler cap’s position and unscrew it. We recommend using a syringe or a special pump to add fresh oil to the transmission oil pan.

Always check the oil level according to the recommendations above to avoid overfilling. Check the oil level in the gearbox of a car at least once every 2-3 weeks. If you do not check frequently, the oil may leak because of damage to the housing body. And repair the gearbox.

What are the symptoms of an overfilled transmission?

With high heat on the road and high mileage of the car, check the oil 20-30 minutes after finishing the engine. The oil will cool slightly, and the readings will be more accurate. You should find work gloves and a dry, soft cloth beforehand.

On many car models, we measure the oil index in the automatic transmission with the engine running. There are many marks on the probe. The first two show typical oil levels. Then perform the following works:

  • Warm up the gearbox. Drive for about 10km and stop on flat ground. Do not turn off the engine and do not press the brake pedal;
  • Keep the brake pedal pressed and change the speed in all positions. We will fill the whole box with oil;
  • Take the probe. It is necessary to check the oil. Hands with gloves open the hood. The probe ring is near the partition that separates the engine compartment from the passenger compartment. It is usually a bright shade. Gently pull the ring and remove the dipstick;
  • Clean the dipstick with a cloth. Reinsert it into the special tube until it stops. You take it out again. A dry place on the lower level will show the amount of oil. If all goes well, reinsert the dipstick and close the cap.

Be sure to check when the engine is hot. If fluid needs to be sufficient after measurement, try not to overfill the system. Excess oil causes foaming. The liquid will foam and increase in volume. Through the vent, it will filter into the box. Look under the car. If you see that everything is dirty with oil, you have spilled too much.

Using a dipstick

By using a dipstick, we perform the following actions:

  • Find a level place for the car and wait for the oil to stabilize. It takes about 15 minutes;
  • Open the hood. Find the probe and extract it. Then, dry with a soft cloth and insert it again. If we could not remove the probe, remove the air filter;
  • Pull out the dipstick again. Let’s look at the indicator. If the fluid level does not reach the maximum indicator, we will add similar brand oil into the hole. Let it rest for a while and look at the indicator. Add more liquids.

Take into consideration that you need to fill the oil in the box above the highest mark. It will avoid the fifth gear drone, which sits above the rest of the car.

Without dipstick

First, install the machine on an overpass and remove the protection. We recommend setting the car on a not very large slope. It will allow you to fill the fluid more than the maximum mark. Now your actions are:

  • Unscrew the filling box. Insert a finger into it. You will feel the oil, as it is on the lower edge of the filler box;
  • Fill the oil with a special syringe. Sometimes it is convenient to use a long pipe. It helps to fill the oil because, in some models, the automatic fill hole is difficult to reach.
  • Checking the oil will not take much time. If you do this work regularly, there is no need for gearbox repair. But if you do not follow it, the amount of oil will decrease because of leaks, which is unacceptable for the car’s normal operation.

It is necessary to check the gearbox’s oil level every 15,000km, and in case we find the oil leaks in the gearbox’s crater.

Important Final Tip

The above sections had explained what happens if you overfill an automatic transmission. One advice we always give to the reader is that you have to change the gearbox’s oil. While some car manufacturers say you should not do this, it is best to do this task to extend your automatic transmission life.

Over time, the oil loses its properties, and even small fragments of metal or other dirt end up in it. Change the oil every 50,000 km if you have the opportunity. If you do not do it now, it may be too late later. If you want to change the oil after 150,000 km, you risk damaging the automatic transmission.

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