How Can I Seal a Transmission Leak?

Checking Transmission FluidHaving a leak in your transmission can be a dangerous thing. It may seem like a few drips here and there won’t end up being a problem, but let’s do the math.  Assuming the puddle is big enough for you to notice, let’s say a puddle about the size of a dollar bill overnight, your transmission would lose about a quart of fluid every 10 days.  If your transmission holds 4 quarts of oil in the pan, then that’s a quarter of your fluid capacity gone in 10 days, and almost all of it gone in a month!

Having low transmission fluid can cause a lot of  expensive and frustrating problems.  First, the lack of fluid can cause higher than usually transmission temperatures.  The fluid in the transmission helps car heat away from friction points.  Less fluid means a higher temperature and a reduced capacity to cool the friction components allowing them to wear faster and potentially fail sooner.  An inadequate transmission fluid level also can mean poor lubrication if there is not enough fluid to reach the critical areas of the transmission also causing premature wear.  Lastly, a low transmission fluid level can cause dangerous drivability issues for your vehicle.  Transmission fluid is the high pressure operating fluid that cause gear smooth and accurate gear changes.  A low level can allow your vehicle to behave unpredictably and possibly even dangerously.

If you maintain your vehicle well and notice the transmission fluid leak, you may consider continuing to top of the transmission fluid level ensuring you don’t end up damaging your transmission due to a low fluid level.  Transmission fluid can range from 8$ a quart up to $15 a quart or more, so every 10 days you’re having to spend that much in replacement fluid, not to mention the time it takes to fill and check your fluid level every few days and continue to go to the auto parts store to purchase more fluid, funnels and clean up materials.

Transmission LeakThe most common leak points on automatic transmissions are the input and output shaft seals.  There is a shaft on the front of the transmission that slides either into the clutch plate or the torque converter that has splines on it.  This shaft transfers power from the engine to the gears in the transmission and will have an oil seal around it.  The output shaft similarly will have a seal that goes around the shaft, a slip yoke or the CV axles depending on the type of vehicle.  As these shafts or axles spin while your drive, over time they can start to wear down the seals around them.  Also, old fluid, low fluid or a lack of driving can cause these seals to dry out, harden or crack causing leaks.


Replacing these seals can often be a costly venture, and depending on the age of your vehicle and how long you intend to continue driving it, it may not be cost effective to replace them entirely.

You do however have another option.  Add BlueDevil Transmission Sealer next time you top off your automatic transmission fluid.  BlueDevil Transmission Sealer is specially formulated to restore the seals on the input and output shafts of your transmission to their original size and soft condition to permanently seal your transmission leak.  BlueDevil Transmission Sealer is guaranteed to seal your transmission leak!  Depending on the speed of your transmission leak BlueDevil Transmission Sealer can pay for itself in 2 weeks or less by saving you money on replacement transmission fluid.

Pick up BlueDevil Transmission Sealer today at your favorite auto parts store like:

  • AutoZone
  • Advance Auto Parts
  • NAPA
  • O’Reilly Auto Parts
  • Bennett Auto Supply
  • CarQuest Auto Parts
  • Pep Boys
  • Prime Automotive Warehouse

Or, purchase BlueDevil Transmission Sealer directly from BlueDevil here.

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6 Responses to “How Can I Seal a Transmission Leak?”

  1. Shane on

    Will this work in Manual Transmission (2007 Ralliart Colt) ? I have a very small leak on my input shaft seal (100ml every 6 months). Currently running Redline 75W90. Does it thicken the fluid at all ?

    • BlueDevil Pro on


      The BlueDevil Transmission Sealer does not harden or thicken in any way. You should add 1 ounce of BlueDevil per every 1 quart of capacity.

      Results should be noticed after about 100 miles of driving.

      Thank You!


    • BlueDevil Pro on


      Unfortunately, the BlueDevil Transmission Sealer would not have any effect on an actual crack in the system. The product is specifically intended to rejuvenate and slightly expand rubber seals/gaskets.

      Thank You!



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