(Updated on May 26, 2022)
A transmission fluid is a special type of lubricant that is formulated to keep the moving components of a vehicle’s transmission running smoothly. There are different types of transmission fluids available, especially for automatic transmissions and manual transmissions.
An automatic transmission needs fluid that not only lubricates its components, but also keeps them cool and brings power to the transmission from the engine. If transmission fluid is old or not adequate enough to do its job properly, then it is going to burn.
Sometimes it could be a problem with the transmission itself in which case you would have to get it rebuilt or replaced. But, in most cases, you can simply replace the transmission fluid with new fluid that is formulated to serve your particular vehicle’s transmission.
What Causes Burnt Transmission Fluid?
The most common cause of burnt transmission fluid is an overheating transmission. A transmission may overheat from a number of reasons.
Sustained High Load
One common cause is running the transmission too hard. If you drive a lot of steep hills, tow heavy loads, or take your car to the track, you may run the risk of overheating your transmission.
These situations are mitigated with external transmission coolers, and some vehicles are even designed with these situations in mind.
Low Transmission Fluid
Another cause of transmissions overheating is low transmission fluid. In addition to filling the valve body, transmission fluid lubricates the internal transmission components.
Running the vehicle with chronically low fluid levels increases your risk of overheating the transmission so check your fluid level and top off the transmission fluid when necessary.
A solenoid is a mechanical component that is controlled by an electrical signal. Inside your valve body, there are many solenoids that regulate the flow of transmission fluid.
If a solenoid goes bad, this could starve your transmission of vial fluid in a given area, causing excessive heat and wear.
Top Symptoms of Bad Transmission Fluid
If you were to keep driving your vehicle while the transmission fluid is bad or burnt, then it will eventually end up ruining your transmission if it hasn’t been ruined already.
To increase your chances of saving your engine, you need to recognize the symptoms of burnt transmission fluid, so you can do something about it as soon as possible. Here are some common signs of burnt transmission fluid.
1) Burning Smell
One of the first symptoms you will recognize is a burning smell inside your vehicle that is coming from your transmission fluid. This burning smell is caused by all the extra friction being created from the gears, which causes them to overheat and burn.
The result is a burning smell that becomes stronger the longer it goes on like that. This is certainly not normal for transmission fluid to be doing that. Transmission fluid should smell sweet and not like it’s burning.
2) Leaking Fluid
If your transmission is leaking fluid, then it will cause the remaining fluid to burn more because there is not enough of the fluid to adequately lubricate the components of your transmission.
This means they will overheat faster as they’re not being adequately cooled down.
3) Trouble Shifting Gears
The transmission is what allows you to change gears. If you have burning transmission fluid, then it will cause more hesitation when you try to change the gears. To make matters worse, the gears may change themselves as you’re driving.
Sometimes you won’t be able to shift gears at all. Regardless of the case, you need to get your car checked over by a professional right away. Your fluid might be burnt or you may be very low on fluid.
If the temperatures of the transmission fluid start to get very hot, then you may even see smoke coming out of the transmission.
This should be a clear enough warning sign that something is wrong and that you need to get it looked at immediately. Don’t continue driving.
5) Transmission Overheated
An overheated transmission may cause all of these other symptoms to happen. Your vehicle may enter limp mode to protect the components, the check engine light may turn on, and you may have to wait a while or reset the ECU until the vehicle can be driven normally.
There are different stages of an overheated transmission that you need to consider, based on how hot it gets. These temperature numbers will be different for each transmission, but below is an example to outline the increasing severity.
If the temperature gets to around 220°F, the metal components of the transmission may have varnish form on them. If it gets to 240°F, then you may run the risk of hardening rubber seals. Hard seals will leak and warrant replacement.
At 260°F, transmission slippage is likely. This could leave you stranded for a while, at least until the unit cools down. If you let the transmission get to 295°F, then your entire transmission may fail and need a rebuild or replacement.
How to Fix Burnt Transmission Fluid
The fix for burnt transmission fluid is very simple: if your transmission fluid has a burnt smell, the fluid needs to be replaced. Whether you need a simple drain and fill or a transmission flush is a matter for debate. This will depend on your vehicle and how long it’s been since the transmission fluid was replaced.
Are you running a transmission with over 150,000 miles on the original fluid? Many shops will recommend you do a drain and fill instead of a transmission fluid flush. In some instances, flushing an old transmission can introduce gear slipping issues on a perfectly functioning transmission. For best results, consult the technician at your local shop.