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Transmission Flush vs Change: What is the Difference?

Virtually every driver knows that an engine oil change is part of routine maintenance. It’s a service that’s meant to remove impurities from the engine, prevent corrosion from the inside out, promote efficient cooling, and keep all your parts lubricated. But what many people forget about is the importance of changing the transmission fluid for very similar reasons.  

Overall, there are two main kinds of service you could perform for your transmission: a fluid flush and a fluid change. There are differences between how they’re performed and what exactly they do. Notably, the price for a transmission fluid flush is around $150 to $250 on average, depending on the type of vehicle and transmission you have, where a transmission fluid change is more time-consuming and the price ranges from around $230 to $475. 

What do these services entail, and is one better than the other? Here’s what you should know about the different types of transmission services

What is a transmission flush? 

A transmission fluid flush is a service that exchanges all the fluid inside the gearbox with new, clean fluid. It’s a procedure that normally takes an hour or less and requires equipment that you’ll find only at a professional shop. At the heart of it, the old fluid is pushed out of the transmission and tranny oil cooler and collected for disposal, then it’s filled with new fluid. 

The idea behind the transmission flush is to remove as many contaminants and impurities as possible with a process that’s fast and relatively not intrusive. 

How a transmission flush is done

Again, the transmission fluid flush needs special equipment to do the job. These are the steps:  

  • Get the transmission to operating temperature with a transmission flush additive mixed with the old fluid. 

  • Disconnect a transmission fluid hose, typically somewhere accessible like the transmission cooler. 
  • Connect the fluid exchange machine inline. 

  • Fill the fluid exchanger with the correct type of transmission fluid for your vehicle. Typically you’ll need twice the volume. 

  • Run the machine. It circulates clean fluid into the transmission while expelling the old fluid into a storage compartment in the machine. 
  • New fluid flushes contaminants out of the transmission as the old fluid leaves. 

  • The new fluid enters the transmission and is topped up to the correct level. 

  • The machine is removed, and the hose is re-connected. 

The transmission flush is almost 100% effective at changing the fluid in the transmission in under an hour. 

What is a transmission fluid change? 

Changing the transmission fluid sounds simpler than a flush, but the process is actually longer and more involved. It takes about 90 minutes for a DIYer to tackle, and you can do it with common hand tools or power tools. The crux of the job is changing much of the fluid as well as changing the filter and getting a read on any issues that could be present. 

What a transmission fluid change includes

A transmission fluid change, on the other hand, does not need specialty equipment and can be performed either by a professional, like at one of our Preferred Shops, or by a DIYer. This is what it looks like:  

  • With the vehicle on a hoist, carefully remove the transmission oil pan.  

  • Be prepared with a drain pan to catch the fluid. It can get messy!  
  • Remove the gasket or silicone sealant from the mounting surfaces, then clean the tranny pan with brake cleaner and lint-free shop towels. 

  • Remove the transmission filter, cutting it open to check for large particles or metal shavings. 

  • Locate the magnet inside the oil pan, checking for excess steel particles or chunks that shouldn’t be there. Clean it off. 

  • Install the new filter, then install the gasket or sealant before re-installing the transmission pan. 

  • Fill the transmission via the dipstick or fill hole in the case to the level indicated in the owner’s manual.  

The transmission service only removed about 70% of the old fluid, but it serves to remove contaminants trapped in the filter and on the magnet. It also re-seals the pan. 

What is the difference between transmission flush vs change? 

Both services are meant to change the fluid, so what’s the big difference?  

A transmission flush is like performing a oil change by draining and refilling the engine oil alone – no filter replacement. A trans fluid flush serves a purpose but it isn’t as thorough. It’s also not as intrusive, and some would argue that it can prevent fluid leaks at the pan gasket. 

And while a transmission fluid change – also called a transmission fluid service – doesn’t remove fluid stored in parts aside from the transmission like the oil cooler, it removes some of the particles that can plug up a filter or continue to circulate in the new fluid. As well, there’s peace of mind that comes from seeing little to no debris stuck to the magnet, or if there is, it’s an early warning sign that can save money on major transmission repair later. 

When should a transmission fluid change be done? 

Generally, a transmission service, whether a fluid change or flush, should be performed around 30,000 to 100,000 miles on an automatic transmission. That’s a wide range, obviously. Specifically, you should identify the interval for transmission servicing for your vehicle based on the information in your maintenance guide, ensuring you adjust for normal or severe service depending on the conditions you drive in. 

Will a flush or fluid change fix transmission issues? 

A transmission flush or fluid change is a preventative maintenance item, not corrective. If you’re already having symptoms or transmission issues, there’s only a slim chance that it could fix what ails you – and that’s if the fluid is low. Odds are very high that transmission symptoms will be due to some type of failure inside the transmission that could be from lack of maintenance, unfortunately. 

What you can do

Is it time to change the fluid in your transmission? We have what you need. Get your transmission fluid at AutoZone and get trusted advice from associates to get the job done right. If you determine the job is too big to tackle, check out our list of Preferred Shops in your area to help you complete the job. 

Frequently Asked Questions

Should I get a transmission flush or change? 

A transmission flush can be a good solution for routine maintenance, but a fluid change offers benefits too. If you can’t afford the full fluid change, at least get the fluid flushed on time. 

What’s the difference between transmission flush and just changing the fluid? 

A transmission flush exchanges all the fluid in the transmission, lines, and oil cooler but leaves other key items untouched. A transmission fluid change also changes the filter and oil pan gasket while changing around 70% the fluid. 

Can transmission flush damage the transmission? 

Performed properly, a transmission flush will not damage a transmission. 

Are transmission flushes a waste of money? 

No! Transmission fluid flushes remove contaminants that could hurt your transmission, much the same way that engine oil is changed to clean the engine. 

Is it good to change transmission fluid on high mileage vehicles

It’s a good plan to maintain a transmission regardless of the mileage on the odometer to keep it operating well as long as possible. 

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