Clean Transmission on Classic Car

Everything You’ll Ever Need to Know About Your Transmission Fluid

By Mark Iafrate - July 4, 2016

What if I told you that your transmission has fluid?! Oh… you already knew that? Well, do you know that flushing your transmission fluid can increase fuel economy, transmission longevity, reduce slippage and make shifting all around easier?

Yeah, now you’re interested. Here’s everything you need to know about your transmission fluid.

Clean Transmission Gear

What is transmission fluid?

Transmission fluid is to your transmission as oil is to your engine. Make sense?

Essentially, it lubricates and draws heat away from the transmission. The only reason you don’t have to change your transmission fluid as often is because the engine oil also has to deal with the leftover dirt and grime from combustion. Well… at least there shouldn’t be any combustion in your transmission.

How do I check it?

Essentially, check the stuff just like you would your oil. Grab a clean cloth and find the dipstick; it’s usually in a hard to find place, so keep looking.

Transmission fluid should be light red or pink in color. Not many contaminants enter into the transmission system, but metal pieces of the gears break off and start floating around in the fluid. This darkens the fluid and is why it eventually needs changing. It can also start to burn and turn black if the transmission overheats.

Okay well, should I flush it?

Maybe! But, don’t do it too often. How frequently you need to flush your transmission fluid depends, largely, on the type of car you own. Some cars want new fluid every 45,000 miles while others don’t ever want it flushed! Seriously, some car manufactures don’t ever call for transmission flushes. General Motors never recommends you flush the transmission fluid in their automatic transmissions. Now, that seems a bit crazy…but, they know best!

The average is around 75,000 miles, but it’s not uncommon for manufactures to recommend every 100,000 miles. The point is, check your owner’s manual.

Transmission Fluid Dipstick Clear

Okay! I’m going to get it changed, or should I get it flushed?

Make sure you know the difference! General Motors, for example, never recommends flushes, but does recommend changes.

For some reason, shops tend to charge an exorbitant amount for a simple transmission change, when a flush is what actually takes work.

Changing your transmission fluid is just as simple as changing your oil. There’s a drain bolt on the bottom and a filter, empty the fluid and replace the filter. Refill it back up, bam. HOWEVER, unlike your motor oil, if you simply remove the filter and let it drain, only about half of the fluid will leave the system. The remainder will be in the transmission still. This is where the flush comes in.

The flush involves removing all of the fluid from the system and usually running some type of pressurized cleaner through it to remove all metal pieces left behind. This is where the big bucks come in. Thankfully, you’ll only have to do this once in your car’s life; twice if you’re lucky, but if the car has over 200,000 miles… do you really want to spend hundreds on a fluid change? Didn’t think so.

Look at your manual and determine which one you need. Usually changes are recommended more frequently, but you can probably skip them all together if your fluid looks good and you remember to actually flush it.

Time to Change TRansmission Fluid

Oops, I forgot to flush my fluid like I was supposed to 50,000 miles ago.

Don’t worry, it’s okay. Well, it might be. Many “car guys” swear on their mother’s graves that if you change transmission fluid years after you were supposed to, your transmission will blow up and die. Okay, well they actually claim that the new fluid gets the transmission so lubricated, that the old metal can’t handle it and quickly breaks down.

Now, there is absolutely NO scientific proof for this. BUT! hundreds, if not thousands, of people claim it happened to them. So there might be some truth to it and conventional knowledge says, “If it ain’t broke, don’t fix it.”

About the Author - Mark Iafrate

5 comments

  1. Thanks for the article. You do not refer to the type of oil to be used. Agents want to sell “their” brand at ridiculous prices. Will it really matter if one uses transmission oil of Engen, Shell, or another oil company? How does Jaguar transmission oil differ from them?

    • Perdo, first of all, thanks for the comment!

      Generally, brand of fluid does not matter. However, it’s vitally important that the type of fluid is correct. There are many types of fluid, which is why most car companies have their own brands or rating systems. If you can find a factory OEM replacement that specifically says it’s made for your car or an equivalent type, you should be perfectly fine.

      Keep in mind though, that transmission fluid isn’t like engine oil where you can get away with a different viscosity. If you’re unsure about the type you need, either do some research or trust the dealership. You shouldn’t have to replace the fluid that often, so it won’t be a reoccurring cost like engine oil.

      Hope that helps!

      • this is my story

        I agree Mark, everything you say.
        I have a Volvo V70 and have found out a lesser known approved oil for my auto transmission is available on eBay for £35.00 GBP, 20 litres, and not the £120.00 I was quoted by my Volvo agent.
        Exchange rate – 04 August 2016, £1.00 = $1.31 US

  2. My cousin recently had some issues with the transmission in his truck. You mentioned that transmission fluid is to your transmission as oil is to your engine. I had no idea that the fluid was so important to the health of the part. I wonder if he has had that checked out yet. Do most mechanics offer services like this?

    • Yes! In fact, most oil change and lube places should be ale to preform a transmission flush or change. It’s not too long of a process. Good luck!

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