Transmission Fluid Change
What is a transmission fluid change or flush?
The transmission fluid change is the tried-and-true process that your owner’s manual specifies when it calls for a transmission service. Your mechanic drains the transmission fluid, replaces the filter, then refills the transmission with fresh, new fluid. The transmission fluid change lets your mechanic get a close look at the transmission pan and the filter. This can reveal the presence of metal particles or other debris, which can indicate a bigger problem that needs to be fixed before it gets worse. This makes the fluid change an ideal preventive maintenance procedure.
The transmission flush process uses a machine to replace an automatic transmission’s fluid. Many auto repair shops own these expensive machines. The old fluid, dirt and sludge is pushed out under pressure, and new fluid replaces it. Flushing usually costs significantly more than a fluid change, due to the cost of the machine. Many shops tend to price the procedure for high profits.
Which should I get, a transmission fluid change or a flush?
The flushing process does not require the pan to be removed or the filter to be changed, so the diagnostic and preventive benefits of seeing what’s in the pan and changing the filter are lost. Additionally, many vehicle manufacturers do not recommend or require include a transmission flush as part of their vehicles’ recommended maintenance schedule. So why do it? Stick with the transmission fluid change that is specified in your owner’s manual.
However, if your maintenance schedule specifically calls for a flush, or your transmission fluid has been ignored for too long and picked up metal particles or other contaminants, a flush is the way to go.
What are the symptoms related to transmission fluid issues?
If your transmission fluid or filter gets clogged, you may notice the engine revving when you're not accelerating the vehicle — this is called transmission slipping. If you notice this, take your car in for maintenance immediately, as the damage will only get worse.
Changing the transmission fluid (and filter, if equipped) typically is a maintenance item, and should be done on a regular schedule. On some vehicles, flushing the transmission is part of the maintenance schedule; otherwise, a flush is only needed if debris is detected in the fluid.
Can I drive with a transmission fluid problem?
Driving a vehicle that has passed the manufacturer specified service interval is not recommended, in general. The vehicle can be safely driven, but skipping maintenance may cost you far more in the long run. If you're past the scheduled maintenance mileage, you should take your car in for service as soon as you can.
If the vehicle has any transmission issues that give you drivability concerns, or any of the symptoms noted here, the vehicle should be towed to a repair facility for diagnostics.
How often do transmission fluids need to be replaced?
Changing the transmission fluid is typically a scheduled maintenance item. Still, transmission issues can happen any time. It is more common to see high-mileage vehicles in poor condition because of neglected maintenance. Performing factory maintenance on schedule is the best way to help prevent transmission failure.
Manufacturers set different service intervals, so be sure to check your maintenance schedule here or in your owner's manual.
How are transmission fluid issues diagnosed?
Transmission fluid and filter changes normally do not require a diagnosis. They are most often completed as scheduled maintenance, or as part of a repair that requires draining the transmission fluid. If the transmission is being diagnosed for other issues, the fluid and filter may be replaced as a step in the diagnosis, or the transmission may require flushing.
How does transmission fluid work?
Like engines, transmissions use oil (or transmission fluid) as lubricant for the many gears and shifting components that drive the vehicle. The fluid used in the transmission is constantly degrading from age, heat, crushing force and high pressure. When it degrades, it becomes unfit for use and must be changed before permanent damage is done to the moving parts of the transmission.
How is transmission fluid replaced?
For many transmissions, the transmission oil pan must first be removed in order to change the fluid and filter. The transmission pan gasket, which is the most common source of a transmission leak, is replaced as part of the service. The filter typically has only a few screws at most, and the transmission pan can be replaced and filled with transmission fluid.
What to look out for when dealing with transmission fluid issues
We recommend using replacement transmission filters that original equipment manufacturer-quality or better. Inferior filters can let through small particles that can quickly damage internal components. By using a quality filter, the transmission is protected from these particles.
There are many types of transmission fluids, and they aren't typically interchangeable. Check your owner's manual to ensure you have the correct fluid for your transmission. If the wrong transmission fluid is added, the resulting damage could be severe.
Can I replace the transmission fluid myself?
The average do-it-yourselfer can change transmission fluid without too much difficulty. The biggest issues tend to be with pumps for European vehicles and over-tightening the transmission oil pan fasteners. As long as you have the proper tools, and the correct fluid has been selected, the job should be dirty but doable.