How to Check Transmission Fluid

First things first, why should you be checking transmission fluid in the first place?

Transmission fluid or oil (the terms are used interchangeably) keep the gears in your vehicle’s transmission lubricated which prevents premature wear. Without lubrication, friction between parts would cause excessive wear and overheating relatively quickly. Having the wrong amount of fluid in your transmission can also cause shifting problems in both automatic and manual transmissions. This is why it is important to check your transmission fluid.

How often should you check your transmission fluid?

I’d like to make it nice and easy and say that you should check your transmission fluid every so many miles. I don’t think it’s quite that cut and dry personally. It’s going to depend on a number of variables.

  • Is it a manual or automatic transmission for instance?
  • What kind of weather do you drive in, is it very hot?
  • Are you an aggressive driver?

These are some things that will affect how often you should check the level of your transmission fluid.

There aren’t really any cold hard facts that say when to check your fluids, but there are some guidelines you can follow.

  • If you have an automatic transmission you can check your transmission fluid pretty easily so I would recommend doing it once a month.
  • If you drive your vehicle hard or live in a hot area, check it more often.
  • A manual transmission is harder to check and you’re not likely to crawl under the car once a month to do it, so as a general rule of thumb I would say check it every time you do an engine oil change.
  • This will allow you to keep an eye on it over a reasonable amount of time.
  • Other times you might check your transmission fluid are when you are noticing any change in the performance of the transmission such as noises, hard shifts, surging, and things like that.

Now let’s take a look at exactly how you check your transmission fluid levels.

How to Check Automatic Transmission Fluid

It’s pretty simple to check the fluid in a vehicle with an automatic transmission because there is a dipstick just like the one used to check your engine oil.

Where the dipstick is located is going to differ depending on whether you have a front wheel drive vehicle or a rear wheel drive vehicle.

  • For a rear wheel drive vehicle the dipstick is located near the rear of the engine, usually on the left hand side but not always.
  • On a front wheel drive vehicle the dipstick is located near the front of the engine.
  • Most manufacturers use a red handle on the transmission dipstick so it’s pretty easy to find.

Before you pull the dipstick you need to do a few things:

  1. Park on a level surface
  2. Start the engine
  3. Place the transmission in Park or Neutral
  4. Let the engine warm up (if it’s not already warm)
  5. With the engine running, you can now pull the dipstick and wipe it off with a rag.
  6. Now place it back in all the way and pull it back out to check the level.
  7. There should be a couple of lines on the dipstick usually a low mark and a full mark although sometimes it will say cold and hot.
  8. Either way you want the oil level to be in between the two marks. Too much fluid can be just as damaging as not enough so be sure to look at both lines.
  9. Add fluid if necessary.

How do you Check Transmission Fluid on a Manual Transmission?

Checking the fluid level for a manual transmission is a bit more involved than an automatic. There is no dipstick to make things easy for you. You’ll have to get underneath the vehicle to check the levels. Just like with an automatic transmission, location will depend on whether you have a front wheel drive or rear wheel drive vehicle. For a rear wheel drive vehicle the transmission is located directly behind the engine, it’s usually pretty evident once you crawl under the vehicle and look.

The picture below is the manual transmission on my 1995 Jeep Wrangler. Don’t mind the oil, it’s a small leak (that’s what Jeeps do)

There will be two plugs on the side of the transmission, a fill plug and a drain plug.  Sometimes they are on the same side, sometimes on opposite sides like my Jeep.

The fill plug is always higher than the drain plug. Most manual transmissions use the fill plug as the check level plug but sometimes you will find a THIRD plug on the transmission for fluid check. These plugs are often labeled with a stamp on the side of the transmission.

If there is any doubt on which plug to use I would wait and consult your manual. If your manual doesn’t give the location then do yourself a favor and purchase a repair manual such as the ones made by Haynes or Chilton.

On a front wheel drive car the transmission is often referred to as the transaxle. The manual transaxle will have a plug on it similar to that of the aforementioned rear wheel drive transmission.

Sometimes you can see the transaxle and it’s corresponding plug from the top of the engine compartment. This makes things much as easier as you don’t have to lift the vehicle or put it on jack stands just to check the fluid levels.

Here’s a picture of our Kia Sportage to give you an idea of what you’re looking at. You can’t see the check plug on our Kia from the top, I could try removing the battery to get a better look.

Again, you might be better served to buy a Haynes or Chilton repair manual to help you with locating the plugs for your specific model of car or truck.

Once you have located the plug you can check your manual transaxle fluid. Whether you have a rear wheel drive or front wheel drive vehicle the procedure for checking the fluid is the same once you’ve found the correct plug. You’re going to remove the level check plug and simply put your pinky in the hole.

Make sure you bend your pinky down a bit and then remove it to see if your finger got wet with transmission fluid. If it did, then you are good to go. If not, try one more time but bend your finger a little more. If despite your best efforts you can’t get fluid on your finger, then you need to add oil to the transmission or transaxle.

It’s important to check your transmission fluid and maintain proper levels in order to ensure trouble free operation of your vehicle. Now that you know how to check transmission fluid, develop a routine for checking it and keep a record. This is especially important if you find yourself adding fluid often.

This is usually a sign that there’s a problem somewhere, probably a leak. If you have a record of when you checked it and how much fluid you added then your mechanic can more easily diagnose the issue.

Checking the transmission fluid regularly will also give you indications of when it might be time for a transmission fluid change.

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