ATF drain and refill how many times?

[RDY4WAR]

1st drain (already done): 4 quarts of old removed, replaced with 4 quarts of new. Sump is 44% new.

2nd drain: 9.5 - 4 = 5.5 x .44 = 2.4 + 4 = 6.4 / 9.5 = 67% new

3rd drain: 9.5 - 4 = 5.5 x .67 = 3.7 + 4 = 7.7 / 9.5 = 81% new

4th drain: 9.5 - 4 = 5.5 x .81 = 4.5 + 4 = 8.5 / 9.5 = 89% new

5th drain: 9.5 - 4 = 5.5 x .89 = 4.9 + 4 = 8.9 / 9.5 = 94% new

You can do this at the same interval as your engine oil change.

 

[RDY4WAR]

On a 25 year old car that the fluid had never been changed I would have not changed it.
I didn't always feel this way but I have seen transmissions fail right after a fluid change on cars that had never been or were over due transmission service...
However, Now thats its been changed I think I would keep flushing or changing a few times till all fluid was clean and bright red.
But I am far from a expert.

That's more of a myth. What usually happens is the owner forgets all about the ATF until the transmission shows a little sign of something wrong like a little excess slip or delay going in gear. They panic and race to lube place for a flush and new fluid. The damage is already done though, and the problem gets worse because no quality of new fluid can repair the damage or stop the inevitable demise. Because people have zero accountability, they want to blame the fluid change instead of their negligence. What will ensure a transmission fails is never changing the fluid.

 

[Jerrysends]

100 miles minimum between drain & fills. I do 3 quarts at a time using an extraction pump. After two times, I freshen up the fluid once every couple years with an additional drain and fill.

 

[daniel327]

Performing multiple drain and fills is a waste of time and ATF as it always results in some old ATF contaminating the fresh ATF. Do the job properly by dropping the pan and cleaning it inside before doing an ATF cooler line flush. Afterwards, refill the transmission with fresh ATF and set the level as per the OEM procedure.

 

[RDY4WAR]

ATF is an incredible cleaner. Once you drive it at operating temp 10 miles, drain and fill it again. Do this until the fluid is all red.

ATF is not an incredible cleaner. It has roughly the same solubility as group III engine oil and contains ~1/10th the amount of detergent. ATF is a glorified hydraulic oil with some FM (or lack thereof) depending on what the wet clutches need. Nothing more, nothing less.

It makes no sense for ATF to be a strong cleaner. There's nothing in a transmission to clean. The internals are not exposed to ambient contaminants nor blow-by gases. The only thing it'll see is some metal and clutch shedding from normal wear which is what the filter is for. No acidic growth to neutralize, no fuel dilution, no dirt/dust, etc... There's just enough detergent (200-400 ppm) and dispersant in there to help that wear material get to the filter.

 

[fozzdesy2001]

Transmission maintenance is THE biggest dilemma that causes massive worry for used car owners! Without knowing what types of abuse the transmission has been through, I spazz every time I do ATF drain and fills on my decades out of date fleet. So far, my Subarus all survived many DF; they all had well over 100K the first time I did one. My new-to-me Toyota is getting the first 2 Quart change this weekend. It will be getting Toyota ATF for 6 quarts total change 2 at a time. 88 Chevy truck is the worst, and for now it aint broke so I will leave it alone (famous last words) 10 quarts of ATF I pretend I bought for something else.

 

[Revving2Redline]

I have to have both filters replaced tomorrow for the first time in over 410k miles. It takes eight quarts of Redline Non Slip CVT Fluid but I am including a ninth one just in case. If i can get some pics, i will post.

 

[midnightlaundry]

On my Vehicle, I disconnect the Fluid Line at the transmission Cooler, and let it pump itself out. That way you get it all except for what's in the Converter. Add a few quarts to roughly flush the Converter and then refill.

 

[Astro14]

ATF is an incredible cleaner. Once you drive it at operating temp 10 miles, drain and fill it again. Do this until the fluid is all red.

Oh, really? What makes it “an incredible cleaner”?

The fact that transmissions are clean inside? They don’t have to contend with combustion byproducts, so, that cleanliness has nothing to do with the fluid itself, which has a lower level of detergents than regular motor oil.

 

[jtwrace]

Oh, really? What makes it “an incredible cleaner”?

The fact that transmissions are clean inside? They don’t have to contend with combustion byproducts, so, that cleanliness has nothing to do with the fluid itself, which has a lower level of detergents than regular motor oil.

That’s correct — the absence of combustion byproducts is the main reason transmissions stay clean, not because ATF is loaded with detergents like motor oil. In fact, ATF typically carries a lower detergent/dispersant treat rate.

What sets ATF apart is its additive chemistry. Formulations commonly include:

• Phenolic and aminic antioxidants to prevent oxidation at sustained high temperatures
• Friction modifiers (often esters) to fine-tune clutch engagement and reduce shudder
• Deposit-control agents to minimize varnish formation in close-clearance valve bodies
• Seal conditioners to maintain elastomer integrity over long service intervals

Because of this, ATF has relatively high solvency compared to many lubricants, and in some cases can soften or dissolve varnish and deposits. That’s why people sometimes describe it as a “great cleaner,” even though that wasn’t its design intent.

 

[Astro14]

That’s correct — the absence of combustion byproducts is the main reason transmissions stay clean, not because ATF is loaded with detergents like motor oil. In fact, ATF typically carries a lower detergent/dispersant treat rate.

What sets ATF apart is its additive chemistry. Formulations commonly include:

• Phenolic and aminic antioxidants to prevent oxidation at sustained high temperatures
• Friction modifiers (often esters) to fine-tune clutch engagement and reduce shudder
• Deposit-control agents to minimize varnish formation in close-clearance valve bodies
• Seal conditioners to maintain elastomer integrity over long service intervals

Because of this, ATF has relatively high solvency compared to many lubricants, and in some cases can soften or dissolve varnish and deposits. That’s why people sometimes describe it as a “great cleaner,” even though that wasn’t its design intent.

Some really knowledgeable folks on this board have listed those ingredients, with the exact opposite conclusion:

That those additives don’t actually help with solvency or cleanliness.

ATF gained a reputation as a cleaner decades ago, when it was made from whale oil - which had a high ester component. But unless you’re buying spermaceti from an illegal market, nobody is getting whale oil in their ATF any more.

I would rather use a good oil and simply change it - but I don’t believe ATF has any special cleaning or solvency ability unless the base stocks contain things like PAO, esters, or ANs. Most don’t, so, I don’t buy the “great cleaner” story.

Back to the OP question - How many drain and fills would I do?

I would do a cooler line flush - put clean fluid in it. It will take less fluid to do a cooler line flush than it will to do several drain and fills.

Then do a drain and fill as convenient to keep the fluid in good shape. Most drain and fills get about 1/2 of the fluid. Slightly less in the case of some transmissions.

The only reason to do a drain and fill over a cooler line flush, is convenience.

 

[KrisZ]

I would drop the pan and change the filter. After that I would not waste time with drain and fills, but use a cooler line exchange and do it all at once.

If “shocking” the system with new ATF is a worry, then doing several drain and fills over a few day span is no different than changing it all at once IMO. I would drive the vehicle for one OCI, or so with one drain/fill and then do the cooler line method.

 

[50yr Street Mech]

Spill and fill every 10k. Change Magnefine inline filter @ 15k, change pan filter every 60k ( only because of the Magnefine inline catching the bulk of the slop ) Overkill ??? Most people say yes. I disagree. Have over 500k on my 13' CRV transmission , 130k on my 03' Toyota, 120k on my 06' Toyota. Expensive ??? Yes....... Another transmission is more expensive than maintenance in my book.

 

[tiredguy]

Hi following up about 2 months later... Last weekend I drained and filled the transmission. The 4 quarts I drained were still very dark, I was very surprised. Someone recommended I save some in a baby food jar to compare. I guess I will do it again in about a month.

 

[50yr Street Mech]

As long as it's still shifting well, keep spilling and filling until clean. In my opinion, you're not changing it fast enough. 2 months is quite a while. Personally, I would change it every few hundred miles. Did you change the filter in the pan ??? ( if equipped ) I know there are a lot of transmissions that don't have an accessible filter, like my old 13' Honda Pilot.

 

[CleanSump]

If it's going to fail it's going to fail. It isn't because of new fluid. This is hearsay from the fact most car owners don't get it done until they have shifting issues and hope the new fluid will fix it. No, it won't fix it nor will it break it.

 

[tiredguy]

As long as it's still shifting well, keep spilling and filling until clean. In my opinion, you're not changing it fast enough. 2 months is quite a while. Personally, I would change it every few hundred miles. Did you change the filter in the pan ??? ( if equipped ) I know there are a lot of transmissions that don't have an accessible filter, like my old 13' Honda Pilot.

I only drove the car a few hundred miles in the last two months.

I didn't drop the pan yet and change the filter.

Originally the transmission would have a very minor stutter when driving in gear not while shifting. It went away after the first spill and fill.

Do you think that the cause of the dark fluid is due to the filter not being changed?

 

[CleanSump]

I only drove the car a few hundred miles in the last two months.

I didn't drop the pan yet and change the filter.

Originally the transmission would have a very minor stutter when driving in gear not while shifting. It went away after the first spill and fill.

Do you think that the cause of the dark fluid is due to the filter not being changed?

Old age and 140k in use makes it dark. Heat cycle as well as breaking down and some clutch . Changing the filter is a good idea though. They do fill and they do get hard and impede flow. Also, I've dropped filters and found the 0-rings/filter seal hardening and ready to break apart.

 

[crashz]

Rdy4War had a good % calculator he posted. The first drain and fill will likely darken enough that you'll barely be able to see a difference. By the third, it will look much better. Keep draining and filling IMO. It won't hurt anything.

 

[50yr Street Mech]

I don't think the " cause" of the dark fluid is a clogged filter, but IMO, the filter needs to be changed regardless. 140K on a filter is quite a lot of miles. Dropping the pan, cleaning the muck laying on the bottom of it, and cleaning the magnets in the pan should help you clean it up faster. I dropped a pan on an 06' Camry with the same problem. 120K. Then I let the transmission drip out overnight after removing the filter. It took 7 qts to fill it back up after putting it all back together. That really cleaned it up quite well. Did one more spill and fill after that, and that was it. The fluid is now red and hasn't turned black since. The filter was so clogged, it tore itself dime size holes in the media to allow ATF to pass through. I never seen a filter in that bad of shape in all my years of servicing transmissions. You won't know the condition it's in until you get in there and do it.