Should I Flush My Transmission?

We don’t recommend it – here’s why:

We have never recommended flushing. Anyone who builds transmissions for a living would never flush their own vehicle. That should tell you something. Manufacturers have begun to warn against flushing stating it could void your warranty.

Transmissions shed metal as they wear. Most transmissions have a magnet in their pan to collect that metal. A fluid inspection is one way to inform you of what is happening inside your transmission. If you're experiencing a problem and you flush out all your fluid, without inspecting the pan FIRST you will have no idea if this is a problem that could have been solved with a minor repair, saving you money.

How Flushing Machines work: Some leave solvents

Flushing machines pressure flush your fluid and all the loose metal particles back through your transmission. Most transmissions have a filter or screen that can plug up with those particles causing it to stop working when it’s flushed. When you don’t inspect the magnet in your pan, you could be flushing chunks through your system causing internal damage. If you have a filter – it needs to be replaced. A screen? It needs to be taken out and washed. They don’t do that when it’s flushed.
Transmission fluid is highly detergent which can wash the varnish off clutches, causing it to slip. Pressure flushing can cause aging seals to start leaking. When it leaks more than a quart it could burn up the unit. Flushing does not cause the transmission to fail but it may speed up the process because it pushed metal particles back through the system.

So if I shouldn’t flush – what should I do? Keeping your fluid fresh lengthens its life.

Vehicles vary – some have filters, screens, internal filters, etc. Some manufacturers will tell you it’s a fill for life or change your fluid every 30k to 60k miles. We recommend changing your fluid every 20k miles. Fluid breaks down like engine oil and when it breaks down then you have metal against metal and that’s when damage occurs. Changing your fluid is the only preventative maintenance you can do on your transmission.

  1. Drop the transmission pan and inspect it.
  2. Wipe it clean.
  3. Clean the magnet and inspect it.
  4. Drain all the old fluid drain out, inspect it, and replace with new.

Some transmissions don’t have a pan you can inspect (Honda’s, Nissan’s, Mitsubishi’s,etc.). They have a drain plug and an internal filter which can’t be changed. So we look at the color and odor of the fluid. Drain the fluid for new as your service.

Transmissions are an intricate piece of machinery. Make sure the technician that is working, servicing or touching your transmission is certified to do so. If a mistake is made and your fluid leaks out it could burn up your transmission. Catching a transmission problem early is the first step toward lowering your repair bill.

Transmissions shouldn’t leak, whine, rev, slam, hesitate or make noise! There are no stupid questions. We welcome your questions and want to help you lengthen your transmissions life. Give us a call: 858-679-8000.

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