How Can I Seal a Transmission Leak? | Autance

The normal operation of your transmission depends on a number of factors. One of them is the amount of fluid…

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How Can I Seal a Transmission Leak? | Autance © How Can I Seal a Transmission Leak? | Autance

The normal operation of your transmission depends on a number of factors. One of them is the amount of fluid circulating in your car’s tranny. A less-than-ideal amount of transmission fluid can lead to problems in shifting. It can also damage your gearbox in the long run. One of the causes of persistent low-levels of transmission fluid is leaks. It is for this reason that vehicle owners should also learn how to fix a transmission leak.

Determine the Cause of the Transmission Leak

There are many potential causes of leaks in your transmission. Some of them are minor ones; although there are also those that are critical. If your leaky tranny happens to be minor, you may only need to top off your transmission fluid with a transmission leak sealer. These are third-party additives that you pour into your transmission fluid port. They are an easy fix and should not cost you more than a couple of hundred dollars.

However, there are transmission leaks that a transmission seal leak product cannot fix. In such instances, it is often necessary to take down the leaking part and replace it with a new one.

Before you attempt to employ a transmission leak fix, it is important to determine what is causing the leak. This will help guide you in the correct action to take.

One of the causes of a transmission fluid leak is deterioration or damage to the transmission fluid pan. Loose rocks and road debris can hit this part of the vehicle when you drive on uneven terrain. It can create small dents or punctures on the pan. Vibrations can also loosen the bolts or the drain plug, especially if it was not tightened using the correct torque. These can lead to transmission fluid leaks.

Broken seals are another reason why you may have a leaking tranny. Seals are not made of durable (read: permanent) materials. They are still subject to wear. Most will crack with the passage of time. Excessive heat also tends to hasten the wearing process. One should always check the different seals in the gearbox. This can be on the input shaft of the system or on the output shaft. It is also wise to check the tail housing seal, the shifter housing seal, the driveshaft, the transmission pan, the plug seals, the speedometer input seal, the valve body, and the sensors.

Sometimes, it is the gasket of the transmission pan that fails. Poor-quality gaskets are more prone to cracking and other types of damage. Transmission leak sealer products may not work if the cracks or the level of gasket deterioration is very severe. You will need to replace the gasket.

It is also possible that the transmission fluid leak is coming from a damaged torque converter. If the needle bearings get damaged or there is a crack in the torque body, then you can have leaks, too. Again, this is a problem that transmission seal leak products cannot address. Replacement will.

Transmission fluid leaks can also be due to cracks in the fluid lines. These are made of durable materials like aluminum and steel. However, accidents happen. These fluid lines can still crack or get damaged.

If you are not sure about what is causing the transmission leak, it is best to bring your car to a mechanic. He can try to inspect the transmission and the associated parts for any sign of deterioration or damage. He can also recommend the most appropriate method on how to fix a transmission leak.

Fix Your Transmission Leak

Once you have identified the cause of the leak, you can proceed to applying a fix. There are two possible fixes, depending on the nature of the leak and its severity.

  • Leak Sealers

There are products on the market that you can put in your transmission to help create a seal on small cracks. These are formulations that contain special additives. When you pour the product after topping off your transmission fluid, these additives penetrate the small cracks. Over time, they form a seal to help prevent the transmission from ever leaking fluid again.

It is obvious that these products will not work on heavily-damaged parts. In general, they are effective in addressing leaks from gaskets and seals due to normal wear. If the cracks or the damage are large, the special additives may not be able to form a complete seal in the gap.

Many of these formulations allow the original seals to return to their normal and original size. They also tend to soften the seals, making them less prone to cracking. It is important to note, however, that different products will come with different formulations. Hence, their mechanism of action may be different, too.

  • Parts Replacement

If the transmission fluid leak is due to a severely-damaged or worn component, then a transmission leak fix will call for the replacement of the part. No instant sealer will ever be able to fix a damaged, cracked, or punctured transmission pan. You can only bring your car to a mechanic and have him remove the damaged pan. You can then install a new one. If you have the spirit of a DIYer, you can perform this fix by yourself.

The same is true with loose thread drain plugs and broken transmission fluid lines. If you have problems with the pan bolts or a worn-out gasket, then you will not have any other choice than to replace these parts. You can spend up to $200 for these parts alone. This does not include labor.

If the problem is in the torque converter, then you can expect the fix to be quite expensive. You will have to replace the torque converter. This requires disconnecting the tranny from the engine so you can remove the torque converter. Auto repair shops can charge you about $600 to $1,000 to have your torque converter replaced.

Fixing a transmission leak can be as easy as pouring a transmission leak sealer. You can also replace the parts that have already deteriorated or damaged beyond repair. These are the only ways you can seal a transmission leak.

Related Post: Best Transmission Additives


  1. Transmission fluid is leaking Inspection Service – Your Mechanic
  2. Transmission Fluid Leak: Causes & DIY – Transmission Repair Guy
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