300000 Miles Never Changed Transmission Fluid

Driving 300,000 miles without changing transmission fluid is not a good thing. If you have driven your vehicle 300,000 miles with the same transmission fluid, you should be aware of potential risks related to the transmission.

After this long period, the fluid gets contaminated and causes serious damage to the transmission. Over time, sludge builds up in the transmission, which damages the transmission severally.

Remember, transmission fluid is the lifeblood of a vehicle’s gearbox. The fluid lubricates, cleans, and cools the transmission and prevents metal on metal collision.

Some owners say that their vehicles operate perfectly without changing transmission fluid. Although everything looks fine, skipping fluid change for long periods will cause sudden transmission failure.

As a result, you will have to perform an expensive repair. That’s why I always recommend changing transmission fluid periodically. Depending on the vehicle model and driving conditions, you should change the transmission fluid between 30,000 and 60,000 miles.

When It is Too Late to Change Automatic Transmission Fluid

The time period of changing transmission fluid depends on your driving type.

If you drive manually, you should change the transmission fluid every 35,000 to 60,000 miles.

But for an automatic transmission system, you should change the transmission fluid every 60,000 to 120,000 miles.

In this sense, the 120,000 miles range appears to be too late to change automatic transmission fluid.

However, many drivers do not change the transmission fluid even after 300,000 miles.

They say it doesn’t affect the transmission operation.

But that is not true all the time. Contaminated transmission fluid increases the chances of transmission’s sudden breakdown.

What is the Difference Between Drain and Flush

Transmission fluid draining means removing the old fluid from the transmission pan.

Generally, it is a less expensive and easy process.

By removing the drain plug, you can drain out the transmission fluid.

In this process, 30% to 40% of transmission fluid drains out.

On the other hand, transmission flush means cleaning the whole transmission system.

Specialized equipment is required to perform the process of pushing out the old fluid and contaminants. This is a complete exchange of fluid.

Should I Drain or Flush My Transmission

Should I Drain or Flush My Transmission

If you never change transmission fluid, you should drain the transmission fluid. For a poorly maintained transmission, flushing is not a good option.

If you flush the transmission fluid after a long time, it will clean the accumulated contaminants and sludge. As a result, transmission slipping or shifting issues occur.

That’s why you should drain the contaminated transmission fluid from the transmission pan only.

Transmission flush is a good option for regularly maintained vehicles, where the transmission fluid changes periodically.

Follow the owner’s manual recommendation to change transmission fluid and vehicle maintenance.

However, if you drive too many miles with a factory fluid, draining or flushing are not recommended.

Because 200,000-300,000 miles after, if you change the fluid, it will cause several issues.

How to Change Transmission Fluid

Follow these 14 steps to change the transmission fluid of your car:

  1. Lift the vehicle using ramps or jack.
  2. Locate the transmission pan.
  3. To catch old fluid, set a drip pan under the transmission pan.
  4. Loosen the transmission bolt and drain fluid carefully.
  5. Put out the transmission pan and check for any wear or damage.
  6. Clean the transmission pan with washer and dry it.
  7. Must replace the pan gasket.
  8. Install the pan again and tighten the bolts.
  9. Now pour the transmission fluid half quark and take a test drive.
  10. After driving, shift the transmission into reverse and park within 2 seconds.
  11. Inspect the fluid level and refill the additional half quark of fluid.
  12. Fill up the transmission fluid according to the owner’s manual recommendation.
  13. After refilling repeat step “10” again to make sure fluid circulates properly.
  14. Finally, drive the vehicle and check if there are any internal issues or leaks.

What are the Symptoms of Dirty Transmission Fluid

There are some common symptoms of a dirty transmission fluid, including:

  • Transmission slipping
  • Burning smell from the transmission
  • Transmission does not shift or shift harshly
  • Unusual noises from the transmission

However, whether you experience the symptoms or not, you should change the transmission fluid regularly to avoid expensive repairs.

What to Do if Transmission is Slipping

If you change transmission fluid after 200k or 300k miles and the transmission starts slipping, few things you can do.

However, there is no guarantee that it will work all the time.

First, reset the Transmission Control Unit (TCU) to fix the slipping problem.

This method will work if your car or truck has automatic transmission.

In automatic transmission, the TCU stores the necessary pressure value for fluid.

That’s why, when you change the transmission fluid, the stored value does not match with current value and transmission starts slipping.

In this case, resetting the TCU will fix the problem.

But if you have a manual transmission, you should check the clutches.

In manual transmission, worn-out clutch causes the transmission slipping issue.

Secondly, you can use a transmission stop slip product.

This will work sometimes when the transmission is poorly maintained.

You can find the best quality products online. But the chances are low to fix the issue if you change fluid after 300,000 miles.

So, think twice about changing or flushing the transmission fluid if you do not change it for a long time.

Should I Change Transmission Fluid After 300k Miles

A highly debated question and the answer is also difficult.

In my opinion, if you have driven over 200K miles and still do not change the transmission fluid, you should not change it even after 300k miles.

This is because, after this long period changing transmission fluid may cause the transmission to slip.

This is the ultimate answer, I think.

But remember that it is a poorly maintained transmission and may require expensive repair at any time.


What color is transmission fluid?

A normal transmission fluid color is red. But with time the fluid turns into dark red and after 80,000 to 100,000 miles brown.

But if you don’t change the transmission fluid for a long time, it turns into a dark black.

Generally, it is not good to continue driving with a contaminated such as dark black transmission fluid.

Because they will increase the chances of several damages.

Does dirty transmission fluid affect gas mileage?

A dirty transmission fluid will affect the gas mileage, but the value is negligible.

If the transmission fluid is dirty, it cannot lubricate the moving parts properly and indirectly cause the engine to work hard.

Therefore, the engine will burn more fuel and reduce fuel mileage by a small amount.

Will transmission fluid clean my engine?

No, the transmission fluid does not clean the engine. The function of transmission fluid is only to clean and cool the transmission system.

It is not related to the engine cleaning system.

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