Stopping a Transmission Fluid Leak

Transmission Fluid LeakStopping a transmission fluid leak starts like stopping any other leak in your vehicle.  You first need to be sure what is leaking and find the source so you can figure out the best plan of attack.  Luckily, your transmission leaks a relatively distinctive fluid so you can often be sure you’ve got a transmission fluid leak simply from the color and smell of the fluid.  Be careful here as some vehicles use automatic transmission fluid in the power steering system so make sure you do not actually have a power steering leak!

The best way to prove you’ve got a leak in a system is to regularly check the fluid level.  If your leak is large, meaning it is leaving puddles, check your fluid level every day. If your leak is small, meaning it only leaves a few drips here and there you can try checking the fluid every week.  If you find the fluid level in your transmission steadily going down you can be sure you’ve got a leak.

The next step is finding out where the fluid is leaking from:

Possible Transmission Fluid Leak Locations

  • Transmission Cooler Lines
  • Transmission dipstick tube O-ring
  • Transmission input seal
  • Transmission output seal(s)

Transmission Cooler Lines

The most common transmission fluid leak location is from the transmission cooler lines.  Every automatic transmission pumps the fluid either through a cooler in the vehicle’s radiator, an auxiliary cooler, or both to help warm the fluid when you first start driving and to help cool the fluid once it has reached normal operating temperatures.  The lines to and from these coolers are simply rubber hoses that can leak at the connection and crimp points. It is usually easiest to find where these lines exit your transmission then follow them up to the front of your vehicle looking for leaks. If you find a leak the best thing to do is replace the line.

Transmission Dipstick Tube O-ring

The dipstick you use to measure the fluid level in your transmission fits into a tube or standpipe.  That tube has an o-ring where it enters the transmission and as that o-ring gets old and dried out it can allow fluid to sneak past it and leak out.  Dipstick tube o-rings often leak intermittently and more when your vehicle is parked on a hill or slope. Replacing this o-ring is often a very easy do-it-yourself job so you may consider tackling it if you find this as your leak location.

Transmission Input Shaft Seal

This is the least common leak point in any transmission because it is hidden behind inside the bellhousing where it is safe from dirt, dust and other things that destroy seals.  If your input shaft seal is leaking then you will see transmission fluid dripping from the front of your bellhousing. If you find a leak here, replacing the seal will require removing your transmission which can be an expensive job.  If that doesn’t make sense for your or your vehicle, use BlueDevil Transmission Sealer to restore that seal and stop the leak.

Transmission Output Shaft Seal

Leaking output shaft seals is a very common leak point.  If you have a transmission fluid leak at the output shaft seal you will see evidence of fluid leaks where your CV axle exits your transmission or where the driveshaft exits the transmission on a rear wheel drive vehicle.  Replacing these seals does not require removing the transmission so check with your mechanic to see if that makes sense for you. If not, BlueDevil Transmission Sealer can seal this leak as well!

You can find BlueDevil Transmission Sealer at any of our partnering local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • Bennett Auto Supply
  • CarQuest Auto Parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Fast Track
  • Bumper to Bumper Auto Parts Specialists
  • S&E Quick Lube Distributor
  • DYK Automotive
  • Fisher Auto Parts stores
  • Auto Plus Auto Parts stores
  • Hovis Auto & Truck Supply stores
  • Salvo Auto Parts
  • Advantage Auto Stores
  • Genuine Auto Parts stores
  • Bond Auto Parts stores
  • Tidewater Fleet Supply
  • Bumper to Bumper Auto Parts
  • Any Part Auto Parts
  • Consumer Auto Parts

Pictures Provided By:

transmission_fluid_leak.jpg – By LoveTheWind – Licensed by Getty Images – Original Link

2 responses to “Stopping a Transmission Fluid Leak

    1. Cherise-

      It is not uncommon, especially in higher mileage vehicles, to have metal shavings/debris in the transmission fluid from normal wear and tear. The best place to start would be to flush your transmission, change the fluid along with the filter and then double check to make sure the fluid level is correct. Having dirty/old transmission fluid or the fluid level too high or too low can cause the transmission to act up and not function properly. Once complete, as long as you are not losing fluid too quickly, the BlueDevil Transmission Sealer would be able to help seal your leak. You should expect to see results after approximately 100-200 miles of driving.

      Thank you!


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