What Happens to Your Automatic Gearbox When You Don’t Replace the Fluid Regularly?

One of the most important and yet also the most relatively simple pieces of maintenance that needs to be done on your automatic transmission vehicle is changing of the transmission fluid. It typically needs to happen at the very least every 60,000 miles, but depending on how much you drive and your driving style, you might find you need to change it more frequently than that. For an exact reading of how often you should change your transmission fluid, you can always check your OEM-provided maintenance schedule.

But what happens when you don’t follow this schedule and you keep pushing back the time when you finally make the change in transmission fluid? What will that inaction do to your car? This is what we are exploring in today’s blog.

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Background: What Does Transmission Fluid Do?

Just as engine oil acts like the lifeblood of your engine, the transmission fluid is doing the same for your transmission. The fluid is especially important in automatic transmissions, which can overheat very quickly if and when the transmission fluid can’t do its main job. The fluid is designed to lubricate and cool simultaneously, allowing the many moving parts of the transmission to move across each other with minimal friction and thus minimal heat and damage.

In addition, the fluid helps to remove metal shavings and other debris that is created in the natural course of the transmission’s operation. It carries these contaminants away and filters them out in much the same way that oil does to contaminants in the engine. Over time, the fluid becomes over contaminated, and will start to gain greater viscosity. When it does, it’s less and less able to either cool or lubricate. That’s the point where you need to change the fluid.

How is Transmission Fluid Changed?

When it’s new, transmission fluid is typically a rich red or pink in colour. Over time, as it becomes more contaminated, it will change to a darker orange/brown colour. You can check the condition yourself on most cars by simply inspecting the transmission fluid dipstick.

In simple terms, transmission fluid is changed in much the same way that the oil is. It is stored in a fluid pan reservoir at the base of the transmission unit. When the fluid can no longer continue to be used, it can be drained from the pan, and then replaced with fresh fluid. The procedure is fairly straightforward, yet it’s still not one of those things that many people attempt to do themselves because they have no way to safely lift the car stably to get underneath.

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What Happens When You Don’t Change It?

Next, let’s look at the consequences that can occur if and when you don’t change your transmission fluid at the right time.

Transmission Overheats

The first and perhaps the most noticeable thing that will happen is an increase in the amount of heat you get from the transmission. You might actually feel this through the shifter when it gets really bad. Since the key function of the fluid is to reduce friction, then not changing it will result in a huge increase in friction as the more viscous contaminated fluid is unable to lubricate the metal parts properly.

You Get Sloppy Shifting

When it’s not properly lubricated and cooled, you’ll notice that what were usually smooth and seamless gear shifts that you had previously have now become very slapdash and strained. You’ll likely feel each one as it groans into position. When you’re using a really advanced system like the Volkswagen 7-speed Direct-Shift Gearbox (DSG), for instance, you’ve invested in one of the most advanced gearboxes. It’s meant to run smoothly, but without fluid, it too could become clunky and clumsy in its shifting.

You Get Gear Slippage

Even when your car gets itself into gear, you will find that it finds it difficult to keep it in the right gear ratio, and you end up with gear slippage. This will become very noticeable when you’re trying to accelerate but you get sluggish and uninspiring acceleration because the gears are slipping and there’s no power where it needs to be. Gear slippage can even become a matter of safety in your car, so replacing the fluid to ensure that it doesn’t happen is very important.

You Have Greater Risks of Leaks

Finally, not changing the fluid when you’re supposed to means that a professional eye is not being cast over your transmission, the fluid pan, and other key components in and around your gearbox. Getting a fluid change is a good chance for a technician to look over the transmission generally to make sure everything looks to be in good condition. Skipping fluid changes can mean you might miss something really important that ends up causing a transmission fluid leak.

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Signs You Need to Change Your Transmission Fluid

To wrap up today’s piece, let’s take a look at the common signs that will inform you that it is time to change over the transmission fluid.

Fluid is in Poor Condition

When you inspect the transmission fluid dipstick — most cars do have them, but not all — you can see for yourself in much the same way you check the oil’s condition. Good transmission fluid is red/pink in colour, and should be silky smooth and free from grit, dirt and other contaminants. If you see that it is turning brown or dark orange, and that it looks grainy, then you are looking at fluid that is either near to or already at the point where it needs to be replaced.

You’re Experiencing Gear Slippage

As we described above, if you are experiencing slippage in your gear ratios and losing power when you are out on the road, then it’s time to contact your mechanic and make an appointment to check the fluid and likely have it changed. If this gear slippage is combined with overheating in the transmission, then you can further narrow down the culprit as the transmission fluid rather than any other component within the transmission system.

You’ve Gone 60,000 Miles with No Change

Finally, if you’ve travelled 60,000+ miles without having changed your transmission fluid, then it’s more than likely you’re due for a change. Check your owner’s manual to see the OEM-recommended maintenance schedule and confirm at what point they say you should change it. If it’s 60,000 miles, then you’re just on time. If it’s 50,000 miles or less, then you are already late and are putting your vehicle at risk.

Never underestimate the value of a transmission fluid change. It’s a simple yet critical piece of maintenance that just needs to get done.