Are you driving and noticing a burning smell from under the hood, or unusual shifting? Your transmission fluid may have burned. Transmission fluid is one of the most important fluids in your vehicle, and when it burns or degrades, you can be in for serious trouble.
Recognizing the signs of burnt transmission fluid early can save you a lot of money in potential repairs and time looking for alternative transportation.
What is Transmission Fluid and Why Does it Burn?
Transmission fluid is a unique fluid that lubricates, cools, and transmits power in your vehicle’s transmission system. Transmission fluid allows all the moving parts to move together in unison without excessive friction or heat.
Unlike engine oil, which can be a variety of different colors, transmission fluid is usually reddish when brand new, and it does so little more than lubricate.
Transmission fluid can be degraded over time because the transmission has higher operating temperatures when you drive. Transmission fluid will start to break down when fluid temperatures begin to exceed 200°F.
When oil reaches 295°F or higher, the oil begins to burn, which destroys its ability to protect the various components in the transmission.
This burning process introduces chemical changes in their oil properties and changes the oil’s color, smell, and most importantly, its ability to do its intended work.
Symptoms of Burnt Transmission Fluid
1. Odd Burning Smell.
There is often a burned transmission fluid and either a burning rubber or burnt toast smell. The burnt smell will probably seem stronger after your vehicle has been on for a while, especially if it’s hot outside or you’ve been in stop-and-go traffic.
You can probably smell it in the cabin, and you’ll smell it when you stand next to the car after parking. Burnt transmission fluid has a unique and acrid smell that is nothing at all like the sweet smell of coolant or the gasoline-like smell associated with engine problems, You will likely remember that smell if you have had issues.
2. Transmission Slipping.
One of the most common symptoms of burnt transmission fluid is when your automatic transmission slips and shows an example of slipping between gears, often while you are trying to accelerate. You may sense that the engine is revving higher than normal before it shifts, or you may feel the car lurch forward suddenly into the correct gear.
This occurs because burnt transmission fluid has also lost its viscosity and pressure necessary to maintain the proper hydraulic pressure for proper gear engagement.
If your RPMs go up and you feel zero increase in speed while driving, or if your vehicle strangely shifts back and forth between gears, burnt transmission fluid could be the issue.
3. Unusual Noises.
Since burnt transmission fluid has lost its ability to lubricate your transmission, possibly grinding, whining, or buzzing noises have started coming from your transmission. These sounds may or may not be present during acceleration, but they usually seem to be more noticeable during shifts.
The ‘sounds’ are occurring because the metal components of the transmission which should be separated by a film of fluid, are either making direct contact with one another or are not engaged properly.
This is not a situation you want to continue. Every time you drive your vehicle, the transmission gets further damaged internally, and small metal particles continue to circulate with whatever is left of your burnt transmission fluid.
#4. Gear engagement Delay.
The delay could actually be how long it takes to shift into drive or reverse after you select a gear? Transmission fluid could be the cause? Sometimes, you may notice that there is a pause or hesitation of several seconds between selecting a gear and actually feeling the car engage.
The transmission needs pressure and transmission fluid to engage the clutches and bands, and if the transmission fluid is burnt, you have an inconsistent pressure.
Pay close attention to how your vehicle reacts when shifting from park to drive in the morning or if it has been sitting for a few hours.
#5. Overheated transmission.
When your transmission fluid burns, this may trigger an overheating cycle of the transmission. You may notice the transmission temp gauge is climbing (if it has one) or a transmission warning light coming up on the display.
Burnt fluid can no longer sufficiently cool the transmission components, meaning they will run hotter than they are designed for.
Excessive heat can warp metal parts and damage seals just like an engine would because it is low on oil. If your transmission is overheating, wait for a safe opportunity to stop the vehicle and allow it to cool off for a while.
#6. Color of Transmission Fluid.
The color of the transmission fluid says a lot. New-ish transmission fluid is normally bright red or pink and fairly transparent. When transmission fluid burns, it darkens a lot and becomes brown and black if bad.
The fluid also has a higher than normal viscosity, and if you are in trouble, it may feel thick and gritty if there are suspended metal particles from transmission components that are starting to wear out.
Measuring the fluid on the dipstick (see how) gives you a good visual indicator of fluid condition right away, and if the fluid is dark, smells burnt, or worst of all, has particles floating in it, you have a problem.
What Does Burnt Transmission Fluid LOOK Like?
The normal, bright red or pink transmission fluid will undergo a transformation as it degrades and is actually burned.
Burnt transmission fluid is often dark brown or black and no longer see-through. The color change occurs from the chemical breakdown that happens when the fluid is exposed to high heat levels.
In addition to changing color, burnt transmission fluid is much thicker than non-burnt fluid. Instead of flowing out like viscous water, it now flows out more like syrup or sludge if it is very burnt!
You may also notice small metal particles suspended in the fluid, which may give a gritty texture. These particles are often small or worn metal from the transmission function, which shows you have internal damage.
When evaluating your transmission fluid dipstick, smear a drop on a white paper towel or napkin to get the most accurate result. If it is new fluid, it will spread with a clear red color, but burnt fluid will do the opposite – it will be dark and will not spread with a clear shape.
What Does Burnt Transmission Fluid SMELL Like?
Burnt transmission fluid possesses a smell that is often described as smelling like burning rubber (or an electrical component), burnt toast, or burnt paper.
A burnt transmission fluid smell is significantly different than the smells of any other automotive fluid; it is not sweet like coolant, nor is it petroleum-based like motor oil. The smell is sharper and acrid than either of those smells, and it is pretty awful and very pungent.
The burnt transmission smell often gets worse the longer the vehicle is driven, especially in hotter weather or heavy stop-and-go traffic.
To put it simply, if you get out of your car after a drive and you smell something burning near the transmission area (which is generally under the center of your car), you should stop and check it out.
Causes of Burnt Transmission Fluid
#1. Low Fluid Levels.
The number one cause of burnt transmission fluid is simply running low on fluid levels. When the fluid levels are low, the remaining fluid will work harder and will heat up faster.
How to fix
Check your transmission fluid levels using the dipstick while the engine is running and warmed up.
If the fluid levels are low, add the manufacturer’s recommended type of transmission fluid until it gets to the “FULL” mark and then check for leaks around the transmission pan gasket, transmission seals, and cooler lines.
#2. Overdue Fluid Change.
Like all fluids, transmission fluid will break down over time due to normal heat cycles and will become less effective at lubricating and cooling.
Most experts recommend changing automatic transmission fluid every 30,000 to 50,000 miles, but a few manufacturers are deeper than that.
The issue is that many drivers don’t stick to these intervals very well. Many drivers are diligent about changing their engine oil in a timely manner, but when it comes to changing the transmission fluid, they simply take a “set it and forget it” approach.
How to fix
Change your fluid at your vehicle manufacturer’s recommended intervals. If a vehicle has burnt fluid but has no major damage, flushing or complete fluid change ( flush the transmission using a qualified mechanic ) can save the function of the transmission.
#3. Too Much Towing or Hauling.
Towing heavy loads regularly places extra strain on your transmission and generates additional heat, which can cause the fluid to burn. This is particularly true when towing up steep grades or in hot weather conditions.
How to Fix It
If you frequently tow, you should consider adding an auxiliary transmission cooler to help dissipate heat, or upgrade your transmission cooler if you already have one, and your transmission fluid temperatures still tend to creep up.
Another great step in the right direction is to use a high-quality transmission fluid and change it a little more frequently than it is recommended.
#4. Overheating Transmission.
Numerous mechanical failures will cause a transmission to run hotter than normal, also burning the fluid, even with correct fluid levels.
A failed cooling system, a stuck torque converter, and clogged transmission cooler lines are common transmission failures that will burn fluid quickly.
How to Fix It
Have a qualified professional check your transmission cooling system, including the transmission cooler, which is usually part of the vehicle’s radiator or a separate unit.
Make any repairs to the failed components, and consider flushing the transmission cooling lines to help remove any debris that might block fluid flow. However, you should be advised that transmission flushes are not recommended in many situations.
#5. Internal Transmission Problems.
Internal component wear, such as worn clutches, bands, or bearings, can create excess friction and heat, which burns fluid from the inside out.
It is commonly believed that this is just an early stage of failure. Sometimes, even the complete failure of the transmission oil pump.
How to Fix It.
This is a job for a professional to diagnose. Depending on the severity of the internal problems, your biggest repair might be a transmission rebuild, possibly even need a transmission replacement.
If you take action quickly upon discovering the burnt fluid, you could stop it from burning up the transmission completely.
Can You Keep Driving?
Driving with burned transmission fluid is much like walking on thin ice. You may be okay for some time, but at some point, something is going to give.
If you burn your transmission fluid, it will not be providing the lubrication, cooling, or hydraulic pressure your transmission needs to work as it should.
In the short term, you could likely drive a short distance or moderately. However, mileage equals wear and tear on all of your transmission components.
What may have only been originally a $150 simple fluid change could quickly become a $3000+ horrible nightmare of a full transmission rebuild or replacement.
If you need to drive with burnt transmission fluid, try to keep it short and avoid anything that is going to generate extra heat. Try to avoid heavy towing, aggressive driving, and minimal stop-and-go traffic as much as possible.
If the symptoms are truly horrible, get the vehicle towed to a shop for repairs, as any other transport, it’s guaranteed to sustain further damage. The cost of the tow will not compare to the price of replacing a whole transmission.