Transmission Fluid: Function, Types And When To Change: A Complete Guide.

1 What Is Transmission Fluid?

Transmission fluid has one primary function, which is lubrication. Lubrication of the internal parts of a transmission, whether automatic or manual. Both require a different kind of transmission fluid, but the purpose is to lubricate the internal parts, reduce friction, and protect the internal parts from wear and tear. But over time, the transmission gets dirty, loses its viscosity, and performs inefficiently; thus, it requires regular oil changes to function properly. 

2 Types Of Transmission Fluid

In general, there are two main types of transmission fluids: Automatic transmission fluid and Manual transmission fluid. These can be further subdivided into the synthetic and mineral transmission fluid. In order to keep your car running properly, it’s important to know which kind of transmission you have and what specific fluid it requires.

Automatic Transmission Fluid

These types of transmission fluid are made for cars that have an automatic transmission, in some cases, modern manual transmissions use the same fluid. Automatic transmission fluid, commonly referred to as ATF, ensures proper operation, performance, and protection of the automatic transmission. This fluid is generally red in color, with the exception of the fluid made specifically for Continuously Variable Transmissions (CVTs). Automatic transmission fluid helps in various functions, such as gear lubrication, torque converter operation, valve body operation, clutch friction operation, brake band friction, and cooling.

Manual Transmission Fluid

Manual transmission fluid in older vehicles, which is sometimes referred to as manual transmission oil or lube, is common in some older manual transmission cars. The key performance and protection factors for a manual transmission include synchronizer compatibility, durability, and shift quality. For this reason, manual transmissions generally use a fluid that is high in viscosity compared to ATF. However, modern vehicles with manual transmissions are compatible with ATF.

Synthetic vs. Traditional Transmission Fluid

While traditional (mineral) transmission fluid is made from crude oil and the reshaping of hydrocarbons for the specifications of different vehicles, synthetic transmission fluid is created through different chemical reactions. A synthetic transmission oil is less likely to break down, oxidize, or lose viscosity at higher temperatures. Synthetic engine oils contain more additives, like corrosion inhibitors, anti-wear additives, and detergents. They are broken down and refined at molecular levels to remove impurities, making them more stable and long-lasting compared to mineral oils. They also reduce sludge deposits, which is an additional benefit when it comes to synthetic transmission fluids.

So how do you choose your transmission fluid? The answer is not necessarily broken down into black or white. It’s always better to refer to your user manual, and when in doubt, consult a transmission specialist. Learn more about the difference between a synthetic, mineral, and semi-synthetic oils to choose the best one for your vehicle. 

3 Benefits Of Synthetic Transmission Fluid

You may have wondered if using synthetic transmission fluid to lubricate your transmission is a better choice than using a conventional type of transmission fluid. There are several advantages of using synthetic transmission fluid over conventional, but before deciding between the two, it is important that you check your vehicle’s owner’s manual and follow the manufacturer’s recommendations. If your manufacturer does recommend the use of synthetic transmission fluid, then by using a synthetic product in your vehicle’s transmission, your car will perform more efficiently and will give you many years of dependable service. Following are the advantages of synthetic transmission fluid over conventional ones.

Better Resistance To Oxidation

A synthetic fluid or oil provides more resistance to oxidation and can even improve your overall fuel economy. Synthetic fluids can retain their viscosity over time and provide better resistance to wear and tear.

Smoother Shifts

A synthetic fluid has the capability of providing your transmission with smoother operation. Because of its superior engineering, the synthetic fluid is better at lubricating your transmission and is able to sustain its viscosity over a broad temperature range. Synthetic fluid performs the same way even at higher temperatures and lubricates the bearings, gears, etc. in a better manner, hence the smoother shifts.

Reduced Cost & Time

As synthetic fluid runs longer and has a higher fluid change interval compared to conventional ones, you save time and money by visiting the mechanic less often.

Extended Transmission Life

Using a synthetic transmission fluid, your transmission will run cooler and cleaner and will be less susceptible to breakdowns. It reduces friction and protects against wear and tear of the internal parts.

4 How Often Should I Change My Transmission Fluid?

Your transmission oil change interval depends upon your type of fluid, vehicle usage, and type of vehicle. Like other automobile fluids, transmission fluid has an expiration date, so you need to keep a record of when the fluid was last changed. However, transmission fluid doesn’t need to be changed as often as engine oil.

Transmission fluid can easily last around 45,000 kms to 100,000 kms, and synthetic oils are good for even more. But an automatic transmission will typically need to have the fluid changed more frequently than a manual transmission.

5 Signs That You Need To Change Your Transmission Fluid

Your car will always show symptoms if your transmission fluid is low or needs to be changed, but you need to know what exactly to look for. Here are the following 6 signs that you should have your transmission fluid checked.

1. Puddles under your car can be an obvious sign of an issue, but they aren’t always related to the transmission fluid. It’s better to get it diagnosed as soon as possible.
2. Roaring, whining, buzzing, or growling sounds when you accelerate or go around a corner are a sign of low fluid level and needs to be checked.
3. If your car is having trouble changing gears or if the transmission starts slipping or sliding, it’s time to check your transmission fluid.
4. When going around corners, the engine revs up unexpectedly.
5. A chattering noise while driving can be caused due to transmission and other problems like worn suspension bushings, steering rods, etc. Therefore, it should not be ignored. 
6. If your car is new, it may throw up a warning light on the dashboard, indicating a low fluid level. In such a case, it’s time to replace or check your transmission fluid level. Your vehicle may also use the “check engine” light to alert you.

6 Is Changing The Transmission Fluid An Easy DIY Job?

It’s a difficult process for the average car owner that necessitates ramps, jack stands, or even a lift. Even then, recognizing the transmission fluid pan and drain plug requires some level of skill beyond a simple engine oil change. Many modern cars have transmissions that are basically sealed shut and require a dealer’s service computer or other specific devices to read temperature or other parameters, making them all but impossible to work on for the average DIYer. However, if you decide to do it yourself, here are some tips you need to follow while doing the job.

7 How To Change Transmission Fluid?

1. Jack up your car using jacks and jack stands so that you can have a good look from beneath and locate your transmission pan.
2. In some cars, you may have a drain plug and a filler plug, which will make your job very easy. You may have to loosen the bolts of the transmission pan to drain the oil if your car doesn’t have a drain bolt. 
3. Place an oil pan underneath the vehicle and drain the fluid from the drain plug.
4. Fill fresh fluid from the filler hole with the recommended transmission fluid and quantity.
5. Take the vehicle for a short spin and check the fluid level once again. If needed, top up.

8 What Happens If You Don’t Change The Transmission Fluid?

Depending on the level of abuse you dole out, unchanged transmission fluid will lead to greater issues. It can evaporate and seep out, causing gasket failure and catastrophic failure. So if you don’t wish to spend a huge amount of money on repair bills, it’s best that you check your transmission fluid time to time.

9 What Is Transmission Fluid Flush?

A transmission fluid change only replaces the existing fluid with a new, clean one. A transmission fluid flush completely removes all old fluid and the leftover gunk and deposits by dissolving them, which usually get trapped in the crevices. Mechanics recommend a complete flush approximately every 100,000 kms. However, this may vary depending on the vehicle you drive, how you drive, and where you drive. During the transmission flush, all existing fluid is pumped out of the transmission system. Once completely drained, brand-new fluid is added, resulting in your transmission running much more efficiently and smoothly.