Most drivers know that the engine needs frequent oil changes to function properly and also know about replacing the braking fluid and coolant after a few years. But because transmissions in modern cars are so long-wearing and changing their oil happens less frequently, many vehicle owners forget to do it altogether.
Still, like all mechanical components in your vehicle, the transmission needs regular care to function smoothly. Thinking about it, the gearbox is almost as complex as the engine, as it contains many gears, shafts, bearings, synchronizers, a clutch, and a shift mechanism, all packaged in a protective casing called the gearbox housing.
On top of that, the gearbox needs lubrication, i.e., transmission fluid, to lubricate the components and minimize friction, dissipate heat, and prevent wear. Without sufficient transmission oil inside, your gearbox will start to wear pretty quickly and might get permanently damaged.
And if a catastrophic failure happens to your vehicle's transmission, it will go nowhere. Namely, the transmission is responsible for converting the engine's high-speed rotational output into a suitable speed and torque for the wheels, depending on the driving conditions. Basically, it allows your vehicle to move forward, reverse, and change speeds smoothly.
So, the gearbox is very important and needs to be optimally lubricated, but how do you check the transmission fluid level in your car? Well, you should really use a dipstick, which can quickly tell you how much oil is left inside. But what if your vehicle doesn't have a dipstick for checking the transmission fluid level? Well, put some gloves on because we will delve deeply into checking transmission fluid without a dipstick!
Safety Precautions: Preparing Your Vehicle for Inspection
You should always prioritize your safety when working on your car. So, when I said that you should use working gloves, I was serious (although I also wanted to add some drama to the text). Also, be sure to put some safety glasses on, as they will protect your eyes from potential splashes of hot oil or other debris while you are working on the transmission.
I also strongly recommend working in a ventilated garage area, as transmission fluid fumes can be harmful if inhaled in large quantities. Although fires don't often happen when you work on the transmission, it's always a good habit to keep a fire extinguisher at hand.
Furthermore, ensure that you have the necessary tools before starting the job. This includes using the right type of wrench or socket for removing the fill plug, as well as using a suitable funnel and hose for adding transmission fluid if needed.
Once you ensure your safety and that you have all the tools you need, here is how to prepare your vehicle for a transmission fluid check:
- Park on a level surface: you can only obtain accurate transmission fluid level readings if your car is level. This will ensure that the fluid is evenly distributed, allowing for a precise reading.
- Engage the parking brake: this will make sure your car remains stable and doesn't move while you are working underneath.
- Turn off the engine: this will allow the oil to settle within the transmission so you can get a more accurate reading, but it also saves you from potential injuries from the moving parts.
- Allow the vehicle to cool: the transmission fluid gets very hot during operation, enough to burn your skin. Thus, I recommend waiting for at least 30 minutes before working on your transmission to minimize the risk of burns. That said, on some vehicles, manufacturers recommend checking the transmission fluid level with the engine running and at operating temperature. If that's the case, be extra cautious to avoid contact with hot components.
Locating the Transmission Fill Plug
Before you even start with the procedure of checking the transmission fluid without a dipstick, it is crucial to find the fill plug. This plug is typically found on the side of the transmission, near the bottom, and is used to add or check the fluid level.
However, the exact location may vary depending on your vehicle's make and model. To locate the transmission fill plug, follow these steps:
- Consult your owner's manual: the manual should provide you with an illustration or description of the plug's location while also giving you the specific tools you'll need to open it. If you are really serious, you can acquire a repair manual for your car online – the same professional technicians use. The repair manual will give you an even more detailed explanation and guide you through the transmission fluid check process.
- Locate the transmission in your vehicle: if the owner's manual doesn't contain a description of the fill plug's location, you can locate it yourself. Start by finding the transmission – it's typically mounted directly behind the engine and is connected to the driveshaft, which transfers power to the wheels.
- Look for the fill plug: it should look like a bolt, a square-shaped fitting, or a recessed plug. Either way, you will probably need a special tool to unscrew it. However, make sure it's not the drain plug, which will be located at the lowest point of the transmission.
- Ensure that the plug you located is the right one: searching online through forums could help you, but you can also recheck the owners or repair manuals.
- Look for the easiest access to the plug: on some cars, you can access the plug directly, but on others, you may need to lift the vehicle using a jack, jack stands, or even ramps.
Cleaning the Fill Plug Area: Preventing Contamination
The gearbox in your car is built with tight tolerances and has gears touching frequently. Even a little bit of debris could cause havoc inside and damage the internal components. Thus, it is crucial that you clean the area around the fill plug before opening it to ensure that no dirt, debris, or other contaminants enter the transmission.
And I don't mean just wiping the area with a towel – you should remove all dirt down to the shiny metal. Here is what I do when refiling transmission with oil:
- Necessary cleaning supplies: have a few rugs at hand, along with a strong brush (even a toothbrush will work) and a degreasing agent or brake cleaner.
- Remove loose debris: use the brush or toothbrush to remove the loose debris from the area around the fill plug. Be gentle but thorough – ensure that you don't damage the casing but also that no dirt is left on the surface.
- Apply the brake cleaner or degreaser: this will help remove the stubborn grime or oil buildup. Let it stay for a few minutes if there is a lot of oil buildup before jumping to the next step.
- Wipe away with a clean rag: use a clean rug, or several of them, if necessary, to remove the grime. Also, apply more brake cleaner if needed to completely remove all the oil and grime.
Removing the Fill Plug and Checking the Fluid Level
Now that you properly cleaned the surrounding area, it's time to unscrew the fill plug and check the oil level. Here are all the steps you need to do:
- Choose the correct tool for your vehicle: the fill plug type wildly varies across car manufacturers. Thus, depending on your model, you will need either a wrench, socket or a specific tool like an Allen or Torx wrench. Make sure you use the correct tool and not some "jerry-rig" solution, as that might damage the plug.
- Remove the fill plug: start loosening the fill plug carefully by turning it counterclockwise. If the transmission fluid level is high, some of the oil might spill on the outside, so have a rag at hand to collect any spill.
- Check the fluid level using a screwdriver (or another long and thin object): ensure that the object is clean before inserting it into the transmission. I often use a screwdriver, but any thin and long object that will fit in the opening will work. On most vehicles, the oil level should be half an inch to an inch (12-25 mm) from the bottom of the screwdriver. However, I recommend checking the correct level for your particular vehicle in the owner's manual, repair manual, or online forums.
Inspecting the Transmission Fluid Condition
Since you have already spent that much time preparing yourself, and your vehicle, cleaning the area, and unscrewing the plug, it is a good habit to also check the condition of the transmission fluid. Much like the oil in your vehicle, the transmission fluid degrades over time and loses its lubricating and cooling properties.
Here are all indicators that point out an aged transmission fluid that needs to be replaced:
- Brown or black color: a fresh, unused transmission fluid is typically translucent red or pink in color. However, as the oil ages and picks up small metal shavings from the gearbox's internal parts, it becomes darker and loses its translucency. A transmission fluid that is brown in color might have a few more thousand miles in it, but since you've opened the plug already, I recommend replacing it with fresh fluid. And if the oil is black and fully discolored, it means it is past its lifespan.
- Gritty fluid: in some circumstances, the fluid might look clean but still contain debris that could be damaging to the transmission. You can check the oil's consistency by rubbing it between your fingers. If you notice grittiness, metal shavings, or debris in the fluid, it could be a sign of internal wear or damage to the transmission components.
- Strong burnt smell: transmission fluids usually have a mild odor that some people even find satisfying. Meanwhile, an aged transmission fluid will have a burnt metallic odor. If your transmission fluid smells like this, you might want to bring your vehicle for an inspection to an experienced mechanic, as it might indicate slipping inside the transmission, excessive wear, or overheating.
If you've never done this before and you are uncertain what the transmission fluid should look like, a good practice I recommend to DIYers is comparing it to a fresh, unused transmission fluid. This will help you assess the color, consistency, and odor more accurately.
Adding Transmission Fluid: When and How to Refill
When you open the fill plug, in most cases, the transmission will have enough fluid. However, if there is not enough fluid inside, or it is already past its lifespan, I recommend refilling the transmission with a fresh new fluid. Here is what you need to do if a transmission fluid refill is necessary:
- Determine the correct fluid type: various transmission types, like a manual transmission, automatic transmission, or CVT, need different fluids to function properly. The fluid type also varies between transmission and vehicle manufacturers. Thus, consult your owner's manual or a professional mechanic to determine the specific type of transmission fluid your vehicle requires. Using the wrong fluid can cause reduced performance and damage to the transmission.
- Use a flexible funnel when pouring the fluid inside the transmission: this will ensure that you don't spill the precious substance!
- Slowly pour the fluid into the funnel and check the transmission fluid level periodically to ensure that you don't overfill the gearbox, as this can lead to foaming, erratic shifting, or other issues. Once you reach the maximum point, reinstall the fill plug.
Reinstalling the Fill Plug: Ensuring a Secure Fit
Just putting back the fill plug won't cut it – you also need to make sure that it's clean. Thus, just like when cleaning the surrounding area, give the plug a proper cleaning with a brush, degreaser, and a rag. That way, you will ensure that debris from the plug doesn't enter back into the transmission.
Also, I strongly recommend using a torque wrench, particularly if the car manufacturer provides torque specifications for the fill plug in the owner's manual. Using a torque wrench will ensure a proper seal without over-tightening the plug.
If you don't have a torque wrench, do the tightening by hand – using power tools is strictly forbidden here, as it might damage the threads and lead to cross-threading. Be sure not to overtighten the plug, as that could also damage the thread.
Finally, make sure you apply a sealant on the plug to stop oil leakage, if necessary. On most cars, the plug has a sealant built in, but it's best to check for your particular model in the owner's manual.
Rechecking the Fluid Level: Confirming Proper Fluid Levels
Once you topped up your gearbox with oil and properly tightened the fill plug, there is one more important step before finishing the job – use the transmission.
This doesn't mean that you should drive your car – you don't even need to remove the jacks! Start the engine and let it run for a few minutes, and then shift through all gears (manual transmission) to ensure that the oil circulates inside the gearbox. In vehicles with automatic transmission, just pause between each gear to ensure that the fluid is distributed evenly.
Once you've done this, let the transmission cool down (if necessary), and follow the same steps for checking the gearbox fluid as before. Adjust the fluid level if necessary – most often, you might need to add a bit more oil to top up the gearbox.
Finally, don't forget to check for leaks! Start the engine again and allow it to run for a few minutes. Inspect the fill plug area for any signs of leaks and address them as necessary.
Maintaining Your Transmission for Optimal Performance
Maintaining the transmission in your car is as important as maintaining your engine. By checking its fluid level regularly and topping up, if necessary, you will ensure its efficiency, longevity, and optimal performance.
By following the steps outlined in this guide, you can confidently check the transmission fluid level and condition without a dipstick, add fluid when necessary, and ensure a secure fit when reinstalling the fill plug.
However, every vehicle manufacturer gives a timetable on when you need to check the transmission fluid and potentially replace it. On modern vehicles, just follow the manufacturer's recommendations on how often to replace the transmission fluid, and you will be fine. However, if you own a car that is more than ten years old, you might want to check the transmission fluid level and quality at least once every year.
You can also use your senses to check for transmission issues. Look for any unusual noises, grinding sounds, slipping, or erratic shifting that may indicate a problem with your transmission. Address these issues as soon as possible by consulting a professional technician to prevent further damage.
Lastly, never use old gearbox oil or a type that the car manufacturer didn't recommend. This is crucial, as the fluid not only lubricates the transmission but it also ensures the correct pressure inside.
Who thought that there are so many things you need to take care of when checking transmission fluid without a dipstick, right? Well, once you get the hang of it, the procedure is quick and shouldn't take more than 30 minutes.
However, novice DIYers don't know about the many associated safety steps, how to check the fluid's quality, or clean the surrounding area, yet they are crucial to getting the job done right. And even if you are experienced, it's good practice to check the necessary steps from time to time just so you don't forget anything.
I hope these steps on how to check transmission fluid without a dipstick are helpful for you and save you some expenses. Still, if all of this looks too complicated for you, there is nothing wrong with bringing your vehicle to a repair shop and trusting a professional mechanic with the job!
I’m Ivo Gievski, the content writer for Tireer. We built our website with over 15 years of experience and extensive research in the automotive and technology sectors. My dedication to delivering high-quality content is unwavering, and I strive to continuously hone my skills to stay ahead of industry trends and provide readers with informative, engaging, and valuable insights.