/Symptoms of Burnt Transmission Fluid
Symptoms of Burnt Transmission Fluid

Symptoms of Burnt Transmission Fluid


The transmission is part of the engine. It can change engine speed and torque. It changes the transmission ratio between the output shaft and the input shaft in a fixed or gradual manner to convert power into torque. The transmission is composed of two parts: transmission mechanism and control mechanism. The transmission mechanism can change the value and direction of torque and speed; The function of the control mechanism is to change the transmission ratio of the transmission, that is, shift to achieve speed change and torque change. If the transmission of your truck fails, your truck will not be able to continue driving.

Working Principle of Transmission

Gearboxes can be divided into two categories. The first is a manual transmission. The key to a manual transmission is that it is composed of gears and shafts, so we can change the transmission torque by changing different gear combinations. The second is the automatic transmission. Automatic transmission is composed of a hydraulic torque converter, planetary gear, and a hydraulic control system. It achieves variable speed and torque through hydraulic transmission and gear combination. The hydraulic torque converter plays an important role in transmission. It consists of a pump wheel, turbine, guide wheel, and other components. The impeller and turbine are a pair of working combinations. For example, they are like two fans, one is the active fan and the other is the passive fan whose blades are driven by the wind from the active fan. The flowing air wind becomes the medium of kinetic energy transmission. If the liquid is used as the medium to transfer kinetic energy instead of air, that is, the pump wheel will drive the turbine to rotate through the liquid, it is necessary to add a guide wheel between the pump wheel and the turbine to improve the liquid transmission efficiency, because the automatic transmission range of the hydraulic torque converter is not large enough and the efficiency is low.

Causes of Transmission Oil Burning

When the transmission of a truck has a burning smell, it indicates that the transmission oil may be burnt. In this case, it must be handled, otherwise, it will increase the potential safety hazard when using trucks. When the truck is driving normally, if you smell a burning smell in the truck, you must pull over the truck immediately and check it. The following are the causes of the scorching of the truck transmission oil.

1. Continuous High Load

One of the most common causes of transmission oil burning is that the transmission runs too hard. If you drive on steep hillsides, tow heavy objects, or drive a truck on the track, the truck may be at risk of overheating the transmission. If we want to alleviate these conditions, we can use an external transmission cooler. Some technicians even take these conditions into account and apply them when designing.


2. Low Transmission Fluid

Another cause of overheating of the transmission is low transmission fluid. In addition to filling the valve body, transmission oil can also lubricate internal transmission components. If the truck owner drives the truck with a low fluid level for a long time, the risk of transmission overheating will increase. Therefore, the truck owner should check the level of transmission oil from time to time and top up the transmission oil if necessary.

3. Bad Solenoid

The failure of the solenoid valve may also lead to the failure of the transmission. A solenoid valve is a mechanical component that is controlled by electrical signals. Inside the valve body, there are many solenoid valves to regulate the flow of transmission fluid. However, if the solenoid of the solenoid valve is broken, it may cause an interruption in the transmission of small bottles of liquid in specific areas, resulting in overheating and wear of the transmission.

Symptoms of Transmission Oil Burning

Without ignoring the possibility of automatic transmission fluid burning, the following key symptoms highlight some warning signals that the truck needs to repair the transmission.

1. Smoke

If the temperature of the transmission fluid starts to get very hot, you may even see smoke coming from the transmission. This should be a clear enough warning signal, which indicates that there is a problem with the transmission. You need to check it immediately and cannot continue driving.

2. Smell of Burning

Once you feel the smell of transmission oil coming from the inside of the truck, the truck owner should be aware that the transmission oil is insufficient or needs to be replaced in time, even if he does not look at it. Similarly, when the gear is overheated due to excessive friction, you will also smell some burning smell. If this is a strong burning smell, it means that the transmission fluid of your truck is abnormal. You can also check your transmission oil. If it is dark and smoky, it is abnormal. You may need to go to a special truck repair shop to check the transmission. The normal liquid should have a unique sweet taste and bright red. If the truck owner does not check and repair the faulty transmission in time, it may cause damage to your transmission oil and tires.

3. Leakage of Transmission Fluid

Transmission oil may leak, or you may notice a low level of fluid in the reservoir. Any leakage of similar transmission fluid is one of the simple methods to identify transmission faults. As the gearbox is a closed system, the fluid should not naturally leak or burn. However, if your truck has difficulties in shifting, it indicates that your gear is dry due to the leakage of transmission oil. Different from automobile oil, the transmission cannot burn or consume any liquid during use. Therefore, running out of transmission oil means that there is a leak somewhere, and other systems of the truck will also overheat due to increased friction.


4. Hard Start

If you can feel that the truck is hard starting when it starts, or the speed of stepping on the accelerator increases during driving, but the truck has no obvious signs of acceleration. It may also be that there is a problem inside the transmission. It may be that the internal lubrication of the transmission is insufficient and the friction between gears increases, which causes the transmission to fail to work normally. At this time, you should go to the truck repair shop in time to check and add gearbox oil to make the gearbox gears lubricated better.

5. Gear Shifting Problems

When you start the truck, you will shift the truck to the “drive gear” as usual. But if you notice that your truck is stationary, or you need to shift gears constantly while driving, it may indicate that you need to repair your truck transmission. Another situation is that when you drive the truck, the gear may slip out, or when you try to shift, it will keep shaking. Any of the above symptoms indicate that the truck transmission needs to be repaired or replaced.


When the transmission oil is burnt, it will show you the obvious symptoms described above. If you notice any of the above symptoms, especially when they occur frequently, it means that you need to check your truck as soon as possible. If these conditions are not handled in time, the burning of transmission oil will cause more serious damage.