Although often overlooked, the transmission is the centerpiece of the powertrain system of your vehicle and, therefore, it’s also one of the most expensive components to repair or replace. That is why it is essential to ensure it’s correctly maintained and to get it fixed at the first sign of malfunction.
Depending on whether your car is equipped with an automatic or manual transmission, the first symptoms to appear when the tranny fluid is starting to get below the minimum level will differ but understanding how transmissions work and what happens when it’s running dry will help you identify where the problem is coming from a lot quicker.
First, here are the most common signs to watch out for that would lead you to a low transmission fluid problem.
Signs Your Transmission Fluid is Low
Lack of responsiveness of the gearbox
An unresponsive, hard to shift, continually staying in gear symptom can happen on both manual and automatic transmissions but with slight differences.
On a manual transmission, a low fluid condition would make the shift stick harder to move, gears harder to engage or a grinding noise could be heard when up-shifting and, most frequently, down-shifting.
On an automatic transmission, whenever the fluid is below a certain recommended threshold, the oil pressure will go down and start giving out bad psi readings. Electronic sensors are located at various points inside your transmission and they are designed to send signals to the onboard computers and receive signals from them. A signal fault between these sensors and the computer can cause difficult speed shifts or the transmission could start slipping.
A slipping condition is even worse since it usually makes the fluid temperature to rise pretty quickly, causing the fluid to oxidize and the fluid will then need to be replaced completely.
Be aware of the fact that a gear changing problem or transmission slipping is not necessarily a fluid level problem. Faulty input and output shaft sensors could also cause the same symptoms and lead to a false diagnosis. We recommend you check the transmission fluid level first if your car is equipped with a dipstick and you feel comfortable enough to do that by yourself. If not, simply bring your car to a repair shop and ask them to check the level. Making sure the fluid level is on point doesn’t cost a lot and it will save you from having to pay for more expensive repairs later on.
Gear shift delays
Delays when shifting gears because of low transmission fluid will only happen on automatic transmissions since manual transmissions use a direct drive system to switch gears. Such a system doesn’t require oil pressure to work, thus the gear shifting operation won’t be affected. At least, for a short amount of time. After a while, a dry-running manual transmission will overheat because of the lack of lubrication until the gears literally start to melt and ultimately seize together.
On the other hand, a delay in gear shifts on an automatic transmission is a clear indication of a dirty, burned out or really low fluid level. Running dry with an automatic transmission is also definitely a bad idea as internal components will wear out a lot faster than you’d ideally like it too.
Any kind of oil leak must always be fixed right away. Not only does a leak will make the fluid or oil level to go down and end up causing something to break due to bad lubrication but it will also cause the oil pressure to drop, sometimes radically. An automatic transmission relies on oil pressure readings to do its job and any unwanted change will have a negative effect on your transmission’s performance.
Blocked or loose piping, improperly mounted components, leakage or obstruction of any of the transmission piping such as the tranny cooler or the high-pressure lines will have adverse effects on the pressure inside the transmission and may cause a variety of problems, such as difficult and longer than usual gear changes.
On a manual transmission, an oil leak won’t be as dramatic and won’t cause bad symptoms at first since it doesn’t rely on fluid to operate but if it’s not fixed, the fluid level will gradually become lower and lower until you start hearing noise when shifting. When this happens, definitive damage could occur to the gears requiring them to be replaced. Might as well say that the transmission unit would need to be replaced as a whole by then.
Noise in neutral position
Grinding noise while in the neutral position, loud or subtle, is usually a sign of low transmission fluid. A low level of fluid also means bad lubrication and gears, bands and clutches not lubricated properly will slowly start to produce a grinding noise when rubbing together. The neutral position is normally the position where your car is making the less noise so it’s easier to hear the grinding then. Be on the lookout for that kind of noise if your transmission just started slipping or taking longer to shift than usual. When in doubt, add a pint of recommended ATF to your tranny and get your car checked as soon as you can.
A lighted up check engine light is a pretty evident sign that something is not working right on your car. If it’s the only symptom you can see and feel and your car still seems to be going great, do not necessarily worry. Most check engine light problems are related to anti-pollution systems these days and won’t always need the car to be stopped right away. If the light starts blinking or if you can detect a smell that wasn’t there earlier, start hearing unusual noises or feel you car driving abnormally, it is better to stop the car and have it towed to the nearest auto repair shop to have it checked by a professional before the situation gets even worse.
How to check your ATF level
In normal operation, your vehicle should never lose automatic transmission fluid. If the level is somewhat lower than it should, there is probably a leak somewhere. Checking the fluid level would be the easy thing to do but most automatic transmissions aren’t equipped with a dipstick these days and may require the assistance of a service professional using the appropriate equipment. Check the owner’s manual or service manual to know if your car is equipped with one and what is the ATF recommended by your car’s manufacturer.
If you are lucky enough that your car does have a dipstick, here’s an example of a standard ATF level checkup procedure. I still recommend you take a quick look at the owner manual though, as most recent cars require more complicated procedure than this one. Some need to be checked hot while others when cold. In park or in neutral. On a few occasions, there are even detailed transmission data displayed in the instrument cluster needing to be set to specific values before the level can be checked accurately.
- Park the vehicle on a level surface and start the engine. Keep the shift stick in the park or neutral position depending on what’s required for your specific vehicle. Allow the engine to warm up to the optimal working temperature. (You should be aware that some transmission fluids are checked with the engine off while other are checked on. Find that info in your owner’s manual).
- Locate the automatic transmission fluid gauge. It usually looks like the engine oil gauge, sometimes in a brighter color or featuring a gear logo on it.
- Pull the dipstick out. Wipe it, reinsert it and pull it out again.
- Your gauge should have two marks for FULL WARM, and FULL COLD. Since your engine is now hot, make sure the level of the transmission fluid reaches the FULL WARM line.
- To add transmission fluid, using a long and slim funnel is best. On most car models, fluid must be poured straight in the dipstick tube. Carefully add transmission fluid in small amounts and re-check the level each time until the fluid reaches the recommended level. Watch out not to overfill the transmission, as draining ATF is a lot more complicated than adding it. Some cars don’t even have a drain plug and removing the transmission fluid pan or using an oil syringe may be required to take out excess fluid.
Do it right, do it once!
With the expansion of constant velocity transmissions, newer transmissions with a higher number of gears and the upcoming of the EV. car transmissions are getting more complex and more expensive to replace every year. The ability to work and fix car transmissions requires mechanics to stay up-to-date at all time and specialized technicians cost a lot more than it used to. Taking care of your car’s transmission and preventing future failures is recommended now more than ever. Buying and using only quality fluid, having your tranny checked on a regular basis and keeping it maintained according to specification is probably your best bet here.
Always remember that, when it comes to cars, cheap is never better. Going for quality stuff always pays up in the end!