How Do You Know If Your Transmission Fluid Needs Changing?
Transmission fluid is among the many critical fluids that help your vehicle to run smoothly. The others are engine oil, coolant, power steering fluid, brake fluid and windscreen washer fluid. You should probably also consider petrol to be a critical component, but it’s not quite the same as the others since its primary function is as a fuel, and not a fluid for engine and transmission health.
In today’s blog, we’re focusing on transmission fluid, and more importantly how you can know when it is time to flush the old transmission fluid and replace it with fresh stuff. First, let’s get some background on Transmission fluid and its function in the car.
What is Transmission Fluid? What Does it Do?
Transmission fluid is responsible for properly lubricating the key mechanical components of your transmission, as well as keeping the system cool, at the right pressure and free from oxidation that could cause rust. If the fluid is not functioning properly, then the entire transmission can come abruptly grinding to a halt, literally. The lubrication and cooling effects that it creates are especially important.
Transmission fluid is circulated through the transmission’s moving parts in a similar fashion to engine oil within the engine. It at once lubricates and cools, preventing unwanted friction and the severe wear and tear that can result from such friction. Also similar to engine oil, it goes into the system fresh in a smooth and silky consistency with a deep, rich red colour. These are key factors in understanding when it’s time to change the fluid, as we’ll explain further below.
Over time, as the fluid does its job, it carries away and filters out metal shavings caused by interconnected parts moving together, as well as other debris and contaminants that are generated through the normal operation of the transmission system. It eventually comes to a point where the fluid is so contaminated that it can no longer function as it should, and needs to be changed.
However, outside of its regular life cycle, there are other factors that can contribute to the need for flushing and changing the transmission fluid. We’ll talk about all the signs in the next section.
Signs That Your Transmission Fluid Needs Changing
The following are the most prominent and common signs that will be shown to indicate that you should have your transmission fluid changed.
1. You’ve Covered 30,000-60,000 Miles on the Clock
The average lifespan for a reservoir of transmission fluid is usually anywhere from 30,000 to 60,000 miles depending on the vehicle and model year. If you’ve noticed that you’ve passed 30,000 miles since your last transmission fluid change, then it’s worth doing some checks to see how the fluid is doing.
For many drivers, this can be done as a quick DIY job at home by removing and inspecting the transmission fluid dipstick. This is another function similar to that of engine oil. On the dipstick, the driver can observe if the fluid is shifting to a more brown/orange colour, or if it is becoming grainy and contaminated. If the fluid is losing its rich, smooth red colour, then it’s time for a change. Crossing the 30,000-mile threshold is a good chance to do that check.
2. Your Mechanic Makes a Recommendation
If you get a recommendation from the mechanic during a transmission service, then following it is the best policy. If you’re worried about a mechanic saying you need to flush the fluid when you don’t need to in order to charge you more money, then you can reflect on the previous point. At the time the mechanic is recommending this course of action, has it been 30,000 miles or more since the last fluid change? If so, you can be sure that it’s being done correctly.
3. You’re Having Trouble Shifting
Another classic sign is when you’re experiencing difficulty in shifting between different settings on your transmission, and/or the car is apparently lagging behind in its gear shifts while you are accelerating. An effective automatic transmission should offer smooth and seamless shifts, especially those made in the last decade or so, and especially those of a more advanced nature like VW’s DSG system. The lag is usually very noticeable, so if you feel it, consult your mechanic and/or check your dipstick.
4. There’s Excess Heat or Even a Burning Smell
Failing transmission fluid will cause added friction within the transmission, which in turn generates more heat. You might be able to feel the excess heat coming up into the passenger cabin around the gear shift, or you might even smell something burning. In either case, slow down, pull over, and investigate.
5. You Hear Revving from the Engine When Cornering
As you take corners, the transmission should once again make seamless shifts to compensate for changes in speed and traction, but when you’re in need of fluid it might struggle and so create excess engine noise and revving noises as you drive around each corner. That excess noise should be easily noticeable.
6. You See a “Check Engine” or Other Warning Light
If your dashboard gives you the “Check Engine” or other engine/transmission warning light, it could well be because of a need to flush and change the transmission fluid, especially if it occurs in conjunction with another factor mentioned in this list. The emergence of the “Check Engine” light should prompt a visit to the mechanic, regardless, because you’ll need to have any OBD-II errors resolved within your car’s system.
7. You Have a Fluid Leak
Wherever your car has been parked for any period of time, check to see if there are any signs of puddles underneath the vehicle. If you notice a red fluid puddling under the car, then you have a transmission fluid leak. Other colours of fluids can indicate other leaks — e.g., green is likely engine coolant — and any leak is bad news. If you are leaking transmission fluid, then either drive very slowly and carefully to a nearby garage, or call out a service to tow your car there.
Conclusion: Most Critical is Regular Servicing
From the above set of important signs, you should be able to surmise that the best way to protect your transmission and keep it running smoothly is to make sure that you have it serviced annually. Proper servicing is the best defense against breakdown when it comes to the transmission.
Your car’s transmission is a complex system and is therefore hard for even a skilled enthusiast to repair by themselves. Key checks on the transmission will spot mechanical faults early and allow them to be repaired before more damage can be done.