6 Causes of Transmission Fluid Leakage (and Repair Costs)

Have you noticed a fluid leak in your driveway that seems to be coming from the automatic transmission, or are you just tired of refilling your transmission fluid?

Then it is definitely time to repair the transmission fluid leak. Repairing transmission fluid leaks doesn’t have to be very expensive, and in most cases it will be surprisingly easy.

In this article, we look at the most common causes of a transmission fluid leak and how much it costs to repair. Let’s look at the most common causes first:

The most common reason for transmission fluid leakage is a bad transmission pan gasket or a corroded transmission pan. If you or your mechanic didn’t tighten the drain plug properly last time, that could also be the cause. It could also come from a leaking seal in the transmission.

Here is a more detailed list of the most common causes of a transmission fluid leak.

6 Common Causes of Transmission Fluid Leakage

1. Faulty transmission pan gasket

A leaking fuel pan gasket is the most common cause of a leaking automatic transmission. The gasket needs to be replaced every time the transmission pan is removed on most car models, but many people reinstall the old one. This can quickly lead to leaks.

It also happens that they get old and start to leak as the transmission fluid slowly eats them away.

Some model car transmissions use a sealant instead of a gasket, which can also wear out and need to be replaced.

2. Cracked or rusted transmission pan

Another common cause of a leaking transmission is a cracked transmission pan. A cracked transmission pan usually occurs if your transmission has an aluminum transmission pan. This can happen, for example, if you hit a hard object under your car on the transmission pan while driving.

Rust is a problem if you have a steel transmission pan. The pans are quite thin in terms of material and if they start to rust, a hole will form quite quickly. Check for signs of rust and if you find any, it’s probably time to replace the pan.

3. Leaking transmission pan drain plug

Not all automatic transmissions have a drain plug, but some do, and if you have one on your transmission, you probably have a leak. You will usually find an o-ring seal on the drain plug, which should be replaced after every fluid change.

Most people don’t replace this o-ring seal when they change the fluid, which causes the transmission to leak after a while.

4. Drive pan bent

If someone before you replaced the transmission fluid and had trouble removing the pan due to, say, a strong sealant, the pan may have bent around the edge.

Steel transmission pans are quite thin and if someone took a large screwdriver to remove them there is a risk that they will bend. Check for damage to the edges of the drive pan. If it is bent, you may need to replace the entire transmission pan.

5. Transmission fluid line

Some automatic transmissions are also liquid cooled, but not all. If you have a refrigerated automatic transmission, you most likely have fluid lines to the transmission cooler at the front of the car.

These pipes are made of steel and often have rust holes and begin to leak. They also often get very close to the pan so you might think it’s a pan leak, but it’s coming from the drivetrain above.

6. Clogged Transmission Hole

Most automatic transmissions have some sort of open transmission vent on top of the transmission to ensure that too much pressure is not built up. These tiny transmission holes can become clogged on some car models, causing transmission leaks everywhere.

Look at the top of the transmission for some breather hoses, or ask your authorized dealer if your transmission has a breather. Since they are installed on top of the transmission, they can be difficult to reach.

Transmission Fluid Leakage Repair Cost

The average cost of a transmission fluid leak is between $100 and $300 depending on the car model and labor costs. You can expect $50 to $150 in parts and the rest in labor.

Here are some examples of repairs that can solve the cost of a fluid leak. Prices include parts, new fluids and labor. Prices can vary widely depending on the transmission model, but it will give you an idea.

Job type Price
Transmission gasket replacement cost (including fluid and filter) $150 to $400
Replace transmission pan (including fluid and filter) $250 to $500
Transmission Pan Drain Plug Replacement $20 to $50
Transmission Fluid Line Replacement $50 to $200

Is it safe to drive with a transmission fluid leak?

Making sure the transmission fluid level is correct will not damage your transmission with a small leak. However, it is best to repair the leak as soon as possible.

The more you drive a car that leaks fluid, the more fluid will drain. At some point you will have nothing left and your transmission will be damaged. If the leak is small, you can buy time to run to the nearest gas station to fix it.

It is obviously terrible for the environment to have a transmission fluid leak so it needs to be fixed as soon as possible.

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