Can Changing Transmission Fluid be Bad?

As a car enthusiast, I like to take care of my ride. This includes periodically changing fluids like Engine oil, brake oil, radiator fluid, and transmission fluid. But, I hear it all the time from mechanics to avoid changing transmission oil if the car’s working fine.

transmission fluid change can be bad

My answer to that is off-course the car is working fine because I regularly change fluids. I hopped on the internet forums to discuss this and got more people saying that I should not bother replacing transmission fluid. This doesn’t make sense to me.

Then one day I came across this youtube video that explained it really well:

So what does he recommends? I learned from this that it’s crucial to change the transmission fluid periodically. But, if your car is a high mileage vehicle (think 94k miles or 150,000 km), and is still running on factory-filled transmission oil, you are better off just leaving it alone.

Fresh transmission fluid has good cleaning properties. This can wash away varnish from the clutch pack, causing clutch slippage. While Flushing the transmission with a machine can damage aging seals, which can cause leakage and hydraulic problems.

You might take chances with transmission oil change but don’t flush the system. If no problems crop up after oil change, then congratulations you have increased the life of your transmission. But a lot can go wrong if you change the transmission oil of a high mileage engine. Let’s see why:

Transmission oil is really thin so that it can move around the crevices of the automatic transmission. As the oil gets old, it becomes thicker and becomes less slippery. Sometimes this extra friction from the old oil is what keeps the clutch working properly. The problem arises when a fresh trans fluid is added to the worn out transmission- The clutch might start slipping or the car might refuse to shift out of gear.

If you have gone ahead, poured fresh oil and now your clutch is slipping. What can you do in this case? Well, you can try using a transmission additive for preventing clutch slippage. Many mechanics recommend Lucas transmission fix additive.

However, it’s best to change transmission oil at around every 50,000 miles (80,000 km). If you regularly do this that you won’t have to wonder if changing transmission oil next time will cause trouble.

Several vehicles nowadays come with lifetime transmission fluid that the company says doesn’t need replacement. But, that’s not really your best choice if you do intend to keep the car for a long time. Car manufacturers usually do to comply with the environmental norms and to show that their cars are low maintenance.

Dual-Clutch Transmission Are Quick But Complex And Difficult To Fix
Dual-Clutch Transmission Are Quick But Complex And Difficult To Fix

Should you Flush or just Change the Transmission fluid?

When you want to change the transmission fluid, you have two choices- Complete flush or Fluid change.

The fluid change means draining the old fluid from the transmission pan and refilling with fresh fluid. Transmission oil flush means taking out old oil from the pan, cooler lines, and from the crevices of the transmission. Flushing is done using a machine.

Fluid change means there will be some percentage of old fluid remaining in the gearbox unit (sometimes up to 50%) but flush ensures that every part of gearbox gets rid of old oil. So, what’s better for you?

As a general rule, if you suspect that you haven’t maintained the transmission well in past, it’s better to just change the fluid and not bother with a flush. That’s because flushing the transmission increases the chance of some gunk getting stuck in the narrow oil channels. And it can even damage the aging rubber seals.

But, if you regularly maintain your car then flush is a better choice as it gets rid of almost all of the old transmission oil. How much does transmission oil change cost?

What Transmission oil should you use?

Just like engine oils, there is a huge variety of transmission fluids available in the market. But it’s extremely important to only use what the car manufacturer recommends.

Different transmission fluid has different base material and additives. Using the recommended transmission oil would mean that the transmission is compatible with it as it’s been tested using this oil.

Read: Different types of automatic transmissions & Different Types of Manual Transmissions

Another video by Scotty Kilmer:

Is it bad to change transmission fluid on high mileage cars?

Changing transmission oil for the first time on high mileage (over 100k miles) car can cause issues. There is a risk of encountering clutch slippage or getting the car stuck in one gear.

What's the difference between Transmission oil change and Flush?

Transmission oil change is draining the old oil from the drain bolt and refilling with new oil. In Flush, a machine is used to push out all the remaining old oil before pouring in fresh oil. Go for the Flushing method only if you regularly change the transmission oil. On high mileage cars, it can damage the transmission.

How much Transmission Fluid Change Costs

A third-party repair shop usually charges between $90 to $150 for a transmission oil change. An authorized dealer would be charging $150 to $250.

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Siddharth Sharma

Siddharth has always been passionate about Cars and Bikes. He was the kind of kid that always had the latest Auto magazine in his school bag. He had this dream- to become a professional racecar driver. Finally, in 2012 he found himself racing as a rookie driver in the Polo R Cup national racing championship. Over time he had to readjust the sail and get into automotive journalism to continue enjoying machines on wheels.