5 Causes of Automatic Transmission Fluid Leaks (and Repair Cost)

(Updated on April 15, 2021)

Your automatic transmission has lots of moving components and parts inside of it. Like with the parts of an engine, the transmission’s moving parts will also generate a great deal of heat as they rub together.

This means that the parts of the transmission will need to be lubricated in a similar way that the engine needs to be lubricated. The only difference is the transmission will use transmission fluid as its lubricant instead of oil.

If you have an adequate amount of transmission fluid in your transmission, then it will be able to lessen the amount of friction between components which in turn keeps the transmission cooler and operating as it should.

Causes of Leaking Transmission Fluid

You can normally wait until you drive anywhere from 60,000 to 100,000 miles before you need to change your automatic transmission fluid. However, you could still lose this fluid if a leak were to occur somewhere in the transmission system before the regular transmission fluid change interval.

The most obvious sign of a transmission leak is if you notice a small puddle of redish fluid underneath your car where the transmission case is. This red fluid is typically associated with transmission fluid although old or burnt fluid will be more of a brown color.

If you see transmission fluid under your car, you need to take it seriously and fix the leak immediately. To help you spot exactly where the leak is coming from, here are the most common locations of automatic transmission fluid leaks.

1) Bad Transmission Pan Gasket

automatic transmission fluid leak

Every automatic transmission vehicle has a transmission pan which stores the transmission fluid. The mechanical seal which rests in between the pan and the transmission is called the transmission pan gasket.

This component is what prevents transmission fluid from escaping as it is transferred into the transmission from the pan. If the gasket were to get damaged or cracked, then it will cause transmission fluid to leak out. What may start off as a tiny crack will likely get worse unless this gasket is replaced.

2) Cracked Torque Pump

The torque pump is what circulates the transmission fluid throughout the entire transmission system. If the pump were to get damaged, then it would either cause the fluid to stop circulating or it would cause the fluid to leak from there.

Either way, you will definitely have a big problem on your hands that needs to get fixed fast.

3) Damaged Transmission Pan

damaged transmission pan

The transmission fluid pan in most cases will last the lifetime of a vehicle. However since the pan is attached to the transmission via fasteners and likely has at least one drain plug, a leak can easily occur if any one of these parts were to become loose or damaged.

In fact, the pan itself could get damaged if you were to get into an accident or accidentally run over a large rock that your transmission pan can’t clear. It may cause a dent or crack in the pan which you may not even be aware of. If you discover your transmission pan is the source of your leak, replacing it is usually the best option.

4) Cracked Transmission Seals

The transmission seals of an automatic transmission keep the hydraulic pressure in-line. The only problem is these seals are constantly exposed to heat as the transmission is in operation.

The seals will eventually get to the point where they will get worn out and crack from all this long-term heat exposure. The seals will then leak transmission fluid.

Any of the seals could be leaking this fluid, including the shifter housing seal, plug seal, tail housing seal, output shaft seal, and so on.

5) Broken Fluid Line

transmission fluid line

The transmission’s fluid line is made to be durable because it is constructed from aluminum or steel material. However, if it were to get damaged because of excessive heat exposure, the line will eventually crack and then it will leak transmission fluid. Even the aluminum or steel material won’t be strong enough to prevent this.

Transmission Leak Repair Cost

If you have an automatic transmission that is leaking fluid, the cost to repair the leak will depend on where the leak is coming from. On average you can expect to pay anywhere from $100 to $250 for the repair job.

However, if the front seal is causing the leak, it will likely increase your repair cost quite a bit since the mechanic will need take out the transmission first to get to it.

5 thoughts on “5 Causes of Automatic Transmission Fluid Leaks (and Repair Cost)”

  1. I have a 1994 Olds Cutlass Supreme S 3.1 and the leak is from the right rear passager side.that leak just started. i did had work done a few weeks ago with a power steering leak and other work done for inspection. I had a slight accident 4 days ago hit my LEFT side.Could that have knocked something loose on the RIGHT side causing it to leak transmission fluid?

    Reply
  2. I had a gasket repair for a transmission leak by Toyota Is a transmission flush necessary after the repair?

    Reply
    • I’d defer to someone who’s seen the car in person to know for sure. If you have enough transmission fluid, you’re probably good to go.

      Reply
  3. i have a 700r4 tranny after the engine has warmed up and turned off the I Lose about 1 quart or more of fluid can this be a problem with the cooling’s line connected wrong or what? I have a small leak in the pan gasket., but its as if someone turned the faucet on. what else could cause this problem? thank Phil 11 25 2020

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