Transmission Fluid Flush vs. Change

Transmission Fluid Flush vs. Change
June 11, 2021

Anyone who knows anything about how to maintain a vehicle knows that it is important to keep clean fluids flowing inside the motor at all times. If not, the fluids — whether we are talking about engine oil, gear oil, hydraulic fluid or transmission fluid — will begin to break down and eventually fall so far out of spec, they begin to cause damage inside the system. 

Not too many people really think twice about taking their vehicle to the shop and asking them to “change the oil.” However, what you think may happen when fluid is changed and what actually happens may surprise you.

Transmission Flush vs. Change

A simple transmission fluid change typically consists of draining all of the old fluid out of the pan, swapping out the filter and adding new fluids back into the system. This is a common preventative maintenance service that gets only the majority of old fluid out, leaving behind remnants that will immediately lower the quality of the new fluid. 

In order to completely remove all fluid from the transmission, you need to perform a system flush rather than a simple change. While a transmission fluid change drains the old fluid from the pan, a transmission flush disposes of all existing fluid in the pan as well as the cooler lines and torque converter.


What Is a Transmission Flush?

A transmission fluid flush forces all of the expired fluid out under pressure via a pump inlet or cooler line flush machine, ridding the dirty fluid from the transmission pan, torque converter and cooler lines. It is followed up with a cleaning agent to help “scrub” clean any residue that may have been hung up. Then, new fluid is added to ensure optimal transmission performance.

Flushing your transmission fluid is a better, more thorough alternative to a basic change, which, of course, means it will also cost you more. However, just because it is the better option, doesn’t mean it is what you need to do every time.

Although transmission maintenance is important, it is different from other systems in an engine in that it doesn’t usually require the same frequency of attention that something like the oil system requires. You may hear different recommendations depending on which mechanic you speak with, but most will suggest that a transmission system needs flushed about every 100,000 miles as preventative maintenance. 


What Are the Benefits of a Transmission Flush?

Performing a transmission flush means experiencing many significant advantages you won’t get with a fluid change:

  • Protect components: Completely replacing your old transmission fluid with new, fresh fluid enables your transmission to run cooler, resulting in maximum wear protection for components like gears, clutches and bearings.
  • Improve shifting: Transmission fluid loses its frictional effects over time, meaning old fluid can result in hard, jerky or hesitant shifting once it becomes worn. Transmission flushes deliver the frictional properties needed to facilitate smoother, more consistent shifting. 
  • Prevent contamination: Old fluid may get left behind in the transmission during a fluid change, contaminating the new fluid and causing performance issues. Transmission flushes eliminate this risk by completely removing all of the old fluid.
  • Minimize clogging: Fluid flushes provide a comprehensive clean to the transmission, preventing sludge and other contaminants from building within the fluid and lodging into the filter. 


What Are the Downsides to Performing a Flush?

While transmission fluid flushes are undoubtedly beneficial, they do come with some downsides:

  • Higher costs: Transmission flushes tend to be more expensive than simple fluid changes.
  • Not a cure-all: Fluid flushes are not an alternative to proper transmission maintenance. A transmission flush cannot fix major issues resulting from a previous lack of maintenance, such as stalling and slipping.
  • Potential fluid movement: Though transmission flushes are perfectly safe procedures, there is a slight chance that eddy currents will cause the fluid to move opposite the normal flow, potentially dislodging debris and transporting it somewhere it shouldn’t be.


What Is the Cost of a Transmission Flush?

If you decide to have a system flush performed on your transmission, it is important to hire a trained professional. If not performed properly, more harm than good can be done to the components of the transmission. 

The cost of a transmission flush will vary depending on who you work with and where you live, but it’s safe to expect somewhere around $200 to be in the ballpark of what it should cost. That’s because fluid flushes require several quarts of new fluid. Transmission flush costs may also vary based on your vehicle type. For example, flushes for smaller vehicles may be in the low $100s, while larger vehicles may cost over $200. 

That may seem like a lot for some as a preventative maintenance fee, but when you compare it to the potential cost of replacing a transmission after neglecting to take care of it, it suddenly doesn’t seem so bad.


What Is a Pan Drop Transmission Fluid Change?

A pan drop fluid change is the process of removing the pan from the bottom of the transmission and draining the fluid through the use of gravity. After removing any debris that has collected in the pan, the filter can be replaced with a new one. 

While the new transmission fluid from a fluid change is more effective than the old fluid, this process only removes about one-third of the old fluid.


When Would You Want to Get a Transmission Fluid Change Instead of a Flush?

If your vehicle has a drain plug installed on the transmission, you can easily perform a pan drop fluid change yourself without removing the pan. This DIY process poses little risk of errors, creates less of a mess and can help you save a considerable amount of money.


How Do You Perform a Pan Drop?

Using a large catch pan, loosen the pan bolts on the bottom of the transmission to cause fluid to ooze out of the transmission and into the catch pan. Then, remove any debris that collects in the pan and replace the transmission filter.

Though fluid changes only remove a third of the fluid, you can drain most of the old fluid from the transmission by driving your vehicle around after your first fluid change and repeating the process two or three more times.


Which Is Best for You?

If you’re unsure whether to get a transmission fluid change or flush, you can refer to your vehicle’s owner’s manual or bring your vehicle to a technician to get a professional opinion. In most cases, if your transmission fluid is especially dirty or it’s been an extended period since your last fluid flush, a technician will recommend a complete transmission flush. If your transmission is well-maintained and the fluid looks relatively clean, a fluid change will likely be sufficient. 


Importance of Transmission Maintenance

Proper maintenance is important for anything you want to last. It is a much more affordable strategy than just waiting for something to break, then getting it fixed. 

A transmission is a very complex system and needs to be functioning at 100% efficiency in order for the rest of your engine to do the same. If you’re looking to get the most out of your equipment, be sure to keep the entire transmission system clean, and keep clean fluids flowing at all times. Whether that requires a system flush or just a simple change is ultimately up to you.


Choose Hot Shot’s Secret Transmission Fluid. High Quality. Less Problems.

When it is time to change your transmission fluid, check out our full line of PAO Group IV base oils. Available in both the Blue Diamond Serve-Duty or Adrenaline Racing Series. We have three Automatic Transmission Fluids (ATF) specifications that cover most trucks on the road today. 

Having issues with your transmission? Find out more about Shift Restore additive for any ATF or CVT. Also, check out the 5 Key Benefits of Using Shift Restore