Draining Transmission Pan: All Fluid Out?

Changing the transmission fluid in your car is a messy and time-consuming job. While there are several ways to go about it, the most common methods are dropping the pan or performing a transmission flush. Dropping the pan is a cheaper option but only removes about 75% of the old fluid. It also requires you to get under the vehicle and remove plastic splash guards or metal skid plates to access the transmission pan. On the other hand, a transmission flush is more expensive but ensures that nearly all the old fluid is removed and replaced with fresh, high-quality fluid. This helps to clean the transmission and protect against wear to clutches, gears and bearings.

A transmission flush is the best way to ensure all old fluid is removed

A transmission flush is a procedure to remove old automatic transmission fluid (ATF), sludge and grime from a vehicle’s transmission and replace it with fresh fluid. ATF is used to cool and lubricate your automatic transmission. Over time, transmission fluid collects foreign particles that can interfere with these functions, causing your transmission to generate more friction and heat. Eventually, these particles can build up into sludge deposits in your transmission and interfere with shifting and acceleration.

A transmission flush replaces 100% of your transmission fluid and purges accumulated particles and deposits from the entire transmission. Fluid is expelled from your transmission using a cooler line flushing machine or a pump inlet. The transmission pan is inspected and cleaned, the filter replaced, and a complete batch of new, pure ATF is added.

A transmission fluid change, on the other hand, replaces only 50%-60% of your transmission fluid. Your transmission pan is drained, inspected, and cleaned, and the transmission filter is replaced and new fluid is added, leaving a mixture of old and new fluid.

While a transmission flush is more expensive than a fluid change, it is the best way to ensure all old fluid is removed. A typical flushing machine uses hoses that connect into the transmission cooling lines. It drains the old fluid and holds it inside the machine while replenishing the transmission with new fluid. Unlike a simple pan-drop, a flushing machine removes just about all the old fluid, including the fluid inside the torque converter.

A transmission flush helps maximize the lifespan and performance of your automatic transmission, which is one of the most expensive vehicle parts to replace. It is recommended to check your vehicle owner’s manual to see how often your manufacturer recommends a transmission flush for your model. Common transmission flush intervals range from every 30,000-50,000 miles to every 3-5 years.

A pan-drop transmission fluid change is cheaper but messier

A Pan-Drop Transmission Fluid Change: Cheaper but Messier

Transmission fluid changes are necessary to ensure the smooth running of your vehicle. There are two main ways to change your transmission fluid: a transmission flush or a pan-drop transmission fluid change. While a transmission flush is a more comprehensive method, a pan-drop transmission fluid change can be a cheaper alternative, but it is messier and more time-consuming.

The Process of a Pan-Drop Transmission Fluid Change

When performing a pan-drop transmission fluid change, you will need to place a large catch pan under the transmission pan to collect the old fluid. It is important to loosen the pan bolts carefully to avoid spilling fluid everywhere. Crafty individuals can try tilting the pan by loosening one corner more than the others, allowing the fluid to drain from a single corner and reducing the mess. Remember to wear safety gear, such as gloves and safety glasses, during this process.

Advantages of a Pan-Drop Transmission Fluid Change

The main advantage of a pan-drop transmission fluid change is cost. Since you only need enough fluid to fill the transmission pan, it is more economical than a full flush. Additionally, a pan-drop can be a good option if you have reservations about flushing old, dirty fluid through your transmission, as there is a risk of dislodging debris.

Disadvantages of a Pan-Drop Transmission Fluid Change

One of the biggest drawbacks of a pan-drop transmission fluid change is that it only removes about a third of the old fluid. This means that you would need to perform three pan-drops to get most of the old fluid out, which is time-consuming. Additionally, accessing the transmission pan can be challenging, especially if you need to remove splash guards or deal with rusted bolts.

In conclusion, while a pan-drop transmission fluid change is cheaper, it is a messier and more involved process. It may be a good option for those who are cost-conscious or prefer to avoid flushing old fluid through the transmission. However, it is important to consider the time and effort required for this method to be effective.

A flush can be more expensive and may not be recommended for older vehicles

Transmission Fluid Flush vs. Pan Drop

Overview

The transmission fluid in your vehicle should be changed periodically to ensure it remains clean and shifting properly. There are two methods for changing the transmission fluid: a transmission flush or a pan-drop fluid change.

Transmission Flush

A transmission flush replaces nearly all the old, dirty transmission fluid with fresh, high-quality fluid. This has several benefits:

• Your transmission will run cooler and receive maximum protection against wear to clutches, gears, and bearings.
• Your transmission will shift more consistently and crisply since the new fluid will provide the correct frictional properties (old fluid loses its frictional properties over time).
• Performing a flush helps clean the transmission and remove sludge and other contaminants that can accumulate due to extreme heat breaking down the fluid.

However, there are also some downsides to performing a transmission flush:

• It is more expensive than a pan-drop fluid change.
• Some people warn against performing a flush on a transmission using old, dirty fluid. The flushing procedure may cause some fluid to flow in the opposite direction of normal, increasing the risk of dislodging debris and causing it to settle somewhere it shouldn't.
• A transmission flush requires additional fluid beyond the transmission's final capacity, which can increase the cost.

Pan-Drop Transmission Fluid Change

A pan-drop fluid change only removes about a third of the fluid, which reduces the performance of the new fluid. It also has some other downsides:

• It can be messy and time-consuming.
• It can be difficult to access the transmission pan on some vehicles, requiring the removal of plastic splash guards or metal skid plates.
• There is a risk of rusted, stuck bolts if you drive in wet, snowy conditions.
• There is a risk of cracking a splash guard during removal or reinstallation.

Recommendation

Whether you choose to perform a transmission flush or a pan-drop fluid change, it is important to service your transmission periodically to ensure its proper functioning. If you have reservations about a flush, especially if your vehicle has an older transmission, it is recommended to go with a pan-drop fluid change instead. While it may be less effective at removing old fluid, it reduces the risk associated with flushing old, dirty fluid through the transmission.

A pump can be used to remove most of the fluid without dropping the pan

Transmission fluid can be removed without dropping the pan, although this method will only remove about a third of the fluid. This can be done through the use of a pump, which can be used to suck the fluid out through the dipstick tube. This method is much cleaner and quicker than dropping the pan, and can be done in a few minutes. However, it is important to ensure that the correct type of pump is used, as some pumps may not be suitable for this task.

One example of a suitable pump is the LiquiVac oil extractor, although there are many other options available on the market. Additionally, it is important to warm up the oil/motor before attempting to remove the fluid, as this will make the process easier.

Another method for removing transmission fluid without dropping the pan is to use a piece of plastic tubing and an air bleeder for brakes. This method involves pushing the tubing down the dipstick/filler tube and using the air bleeder to draw out the fluid. This method is also quick and mess-free, and can be applied to many different applications.

It is worth noting that, while these methods are effective for removing most of the fluid, they will not completely drain the torque converter. For a complete transmission fluid exchange, it is necessary to remove the line from the transmission to the transmission cooler and run the engine to flush the torque converter.

Additionally, it is important to consider the maintenance history of the transmission when deciding whether to perform a flush or a pan-drop. If the transmission has been treated roughly or has a sketchy maintenance history, it is recommended to visit a professional and have the transmission flushed. On the other hand, if the transmission has been maintained well, a series of pan-drops may be more suitable.

Flushing machines use new fluid to flush out old fluid

Dropping the transmission pan does not get out all the fluid. This method only removes about a third of the fluid, which can reduce the performance of new fluid. It is also a messy and time-consuming process.

Transmission flushing machines use new fluid to flush out old fluid. These machines typically use hoses that connect to the transmission cooling lines. They drain the old fluid and hold it inside the machine while simultaneously replenishing the transmission with new fluid. This process ensures that nearly all the old fluid is removed, including the fluid inside the torque converter.

The benefits of a flush are clear: all the old, dirty fluid is replaced with fresh, high-quality fluid. This helps the transmission run cooler and provides maximum protection against wear and tear on clutches, gears, and bearings. It also improves shift consistency and quality. Additionally, performing a flush helps clean the transmission by removing sludge and other contaminants that accumulate due to extreme heat breaking down the fluid.

Some flushing machines, like the Mahle ATX-2, even offer the option to piggyback a power steering flushing unit, providing a 2-in-1 machine. The Mahle ATX-3 offers the option of exchanging fluid through the dipstick tube with a probe. The Robinair transmission oil exchanger is another example of a flushing machine that can exchange the fluid in the pan before it passes through the transmission filter, preventing damage to other engine components.

The cost of a transmission flush can vary depending on factors such as the vehicle's size, the transmission's total-fill capacity, and the cost of the transmission fluid. The procedure requires additional fluid beyond the transmission's final capacity to fill the machine reservoir and lines, which contributes to the overall cost.

Frequently asked questions