Too little transmission fluid can cause many problems and even damage your transmission.
Your transmission uses the transmission fluid for various purposes. Mainly it is used as hydraulic fluid and it transfers power with your torque converter between the gears and the engine. It is also used to lubricate, clean and cool your transmission parts.
If you are suspicious about the level of your transmission oil, you should always check it as soon as possible. If you drive too far with too little transmission fluid, your transmission may fail due to overheating or lack of lubrication.
Low Transmission Fluid Symptoms
There are many possible symptoms of low transmission fluid, but here are the most common ones.
1. Gear Slippage
The most common symptom of fluid with a low transmission level is the slipping of your transmission. Your transmission requires hydraulic pressure to connect the power between the engine and your wheels. When this pressure becomes too low, the transmission slips, and you can tell this by the fact that the engine speed is higher than usual when you are driving.
2. Shifting problems
The transmission requires a stable and correct fluid pressure to change gears for you. If the fluid level in your transmission is low, the transmission may have difficulty building up the correct pressure needed to shift gears properly. In some cases, the transmission may not shift at all and get stuck in a gear.
3. Late engagement
If you have a low transmission fluid, it can lead to late engagement between gears. When you put your gear lever in neutral or driving mode, it must build up pressure before the car starts moving. If the fluid level is low, it may take a long time for the pressure to build up in the transmission and converter. If the fluid level is low, you will often get a delay of 2-3 seconds.
4. Erratic Shifting
Low transmission fluid can lead to delayed or, conversely, rapid shifting of gears. If the transmission fluid level is low, the hydraulic pressure may be unstable. A transmission requires stable hydraulic pressure to engage the gears as required and to ensure smooth gear changes. If the pressure is too low or jumps up and down, this will result in shifting that is too hard or too slow. This can be caused by a faulty shift solenoid.
5. Overheated transmission
Your transmission fluid helps to cool all rotating parts within a transmission. Friction generates heat and there are many gears and moving parts in a gearbox. If the level becomes too low, there is not enough time for the transmission fluid to cool down before it is time for another revolution through the transmission. Some transmissions also use coolant from the engine, which can cause the transmission to overheat if the engine overheats.
6. Engine light ON/Limp mode
The transmission uses many electrical sensors and solenoid valves. When the transmission control unit detects a fault, it stores a fault code in the transmission control unit. With some codes, it also sends a signal to the engine control unit to turn on the engine light.
If your engine light is on and the ECM detects a serious problem, the engine control unit could also put the engine and transmission in limp mode. Limp mode may cause your transmission to shift only through the first three gears. It may also cause your engine RPMs to become limited.
Low Transmission Fluid Troubleshooting Table
|Low transmission fluid||Gear Slippage|
|External Fluid leak of the transmission||Replace transmission pan gasket. |
Replace axle seals.
How to check the transmission fluid level
The most common way to check your transmission is with the transmission dipstick under the hood. However, some vehicles and transmissions do not have a dipstick, so you may need to check it with an OBD2 scanner or with special tools provided by the manufacturer.
If you need to check the transmission fluid level parameters in the engine control unit or the transmission control unit using an OBD2 scanner, you can use this manual in the same way as you would use a dipstick. If you cannot find a dipstick and wish to check your transmission fluid, call your dealer or ask us on this website.
This guide is a general guide applied to the most common transmissions. Your transmission may be different and you should always check your repair manual first.
How to check the transmission fluid level:
- Start the engine and let it idle.
- Wait until the transmission gets to around 40C. You can see this with an OBD2 scanner in the parameters.
- Check your transmission dipstick while the car is at idle. In most cases, you should check the transmission fluid with the engine at idle. The level should now be between the MIN and MAX marks. If your transmission fluid lower than MIN/at MIN, it’s time to refill.
- Refill your transmission and do the same procedure again to check your transmission fluid level (Read the next topic first).
How often do I have to fill my transmission fluid?
Never. The transfer fluid system is a sealed system and should never need refilling. If you have a low transmission fluid level, the transmission is most likely leaking somewhere.
The most common leakage occurs at the gasket between your transmission fluid sump and the transmission. If your transmission oil level is low and you can see that the leak is coming from the sump, I recommend that you repair it and replace the fluid at the same time.
On some gearboxes, the transmission fluid filter is in the sump and you will still need to remove it. For best results, you should always repair the leak before you refill the fluid. If your fluid level is low, there is a chance that the leak is not so small.
If you want to learn more and go deeper into transmission problems, you can read our article Transmission Problems.
Too little transmission fluid leads to low or fluctuating pressure in your transmission and can cause many different problems when shifting.
The fluid is also used as a coolant and lubricant for your transmission, and a low fluid level can cause serious damage to your transmission. I recommend that you repair the leak and replace the transmission oil if you find that your fluid level is low, to avoid future problems.
If you have further questions about your transmission that are not answered here, please leave your comment below and I will answer you as soon as possible. You can ask all other questions about your vehicle on our website.