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Top 5 Transmission Fluid Leak Causes and How to Fix Them Safely

You back out of your driveway and see an oil spot. But wait—is that oil, or is that a spot from a transmission fluid leak?

If your transmission is leaking fluid, you should figure out what is causing the leak and the best way to fix it. Inadequate fluid levels will cause the transmission to slip or seize. To avoid expensive repairs, maintaining your vehicle’s transmission is critical.

Manufacturers recommend that you check your transmission fluid every 40,000 miles. Look in your owners’ manual to locate the transmission dipstick. If it is low, do not drive the vehicle until you can fix the leak and replace the fluid. 

What Causes Transmission Fluid Leaks

If your transmission is leaking, you must not ignore the problem. You need to get a leak checked immediately. Repairs increase in cost the longer you wait, and you can cause irreversible damages to vital mechanisms in your vehicle. 

You can determine the best way to fix the leak if you know the cause. Whether you do it yourself or hire a professional. These are the most common causes of transmission fluid leaks: 

  • Transmission pan or drain Plug
  • Broken seals
  • Transmission pan gasket fails
  • Torque converter leak
  • Cracked fluid line

When it comes to a transmission leak, do not wait for a minor repair to become a costly one. Knowing the early signs will help you find the best way to stop a transmission leak. 

transmission stop leak

Top 5 Ways How to Fix Transmission Leaks Safely

The cost of fixing a transmission fluid leak is between $150 and $200—as long as there is no need to take off the transmission to make the repairs, that is. Some experts even say it could cost as much as $1,000.

If you think that your vehicle is worth the cost, then knowing the best ways to make these repairs will help. Take a look at the five most common ways to fix a transmission leak.

1. Locate the Leak 

To fix the leak, you must first find it. Raise the vehicle using a lift or jacks and take extra caution to ensure the car is adequately supported. Once you have done this, you can look under the vehicle to locate the leak and see what type of repair will be needed. You may determine the repair requires a mechanic.

If you are unable to locate the leak right away, experts recommend using talcum powder. You will use this to follow the flow pattern. 

2. Determine the Cause 

Once you see the leak, you can determine what is causing it. For example, if your transmission pan gasket fails, you know to replace the gasket. You may also discover that the leak is caused by a component you are not capable of repairing. Sometimes you will need a mechanic just to diagnose the cause of a transmission fluid leak.  

stop transmission leak

3. Consult a Repair Manual or Database 

Car experts agree that you need to consult your vehicle’s repair manual for instructions on fixing your car yourself. You can easily find one online.

With online car repair databases, you can watch videos from technicians who can virtually assist you with your transmission repair. Some databases even offer places to ask the technicians questions directly.    

4. Replace All Seals, Lines, and O-rings

A transmission has shaft seals, gaskets, plugs, and the dipstick has an O-ring. All of these materials are made of rubber and erode over time. Replacing them is the best solution, and you can do it yourself. The parts you need can be found at any auto parts store. 

The transmission is the second most significant vehicle component. If it does not run, your car does not drive. If it overheats, it will seize. Transmission cooling lines are crucial to keep the temperature of the transmission in the proper range. They are one of the most common causes of fluid leaks

5. Use a Transmission Sealer

A transmission sealer is a liquid sealant that creates an air-tight bond that stops leaks. It is formulated to restore the input and output shaft seals. It is also designed to bond with the aluminum and steel components to stop leaks inside the transmission.

Some repairs cannot be made with a sealant, but you may be surprised at what you can fix with a liquid sealer. 

The Dangers of a Transmission Fluid Leak 

Transmissions require lubrication to run efficiently. Proper fluid levels improve fuel economy and ensure your warranty remains valid. Financially, the risks of not repairing a leak in your transmission can be in the thousands. If a fluid leak leads to a transmission rebuild, you are looking to spend around $3,500.

The leak in your transmission creates hazards that most people do not think about. This includes dangers to the environment.

Transmission fluid is not biodegradable. If it gets into a water supply, it can cause those drinking the water to get sick. Animals who consume transmission fluid can die if left untreated. They die of kidney failure, often within 24 hours of ingesting.  

It is also a danger because transmission fluid is highly flammable, it causes vehicle fires. It has also reportedly caused house fires from leak spots on the driveway that were not cleaned.  

transmission fluid leak  

What to Do When You Can’t Stop a Transmission Fluid Leak 

Now that you have figured out the cause and how to fix your transmission fluid leak, you must determine if it is worth putting in the money, the time, or the energy into these repairs. If you have an older vehicle, you are likely to continue to run into maintenance issues. Repair costs will continue to increase, and eventually, it will not be worth keeping your car.

If you have decided to get rid of the car rather than fix it, you have options. You could donate the car, wholesale it for parts, or sell it to a place that buys junk cars for cash.