Flush vs. drain/fill

[ericthepig]

I haven't haunted this ATF forum much (if at all) in my years on BITOG - but now I humbly enter here with a question. I did a bit of searching (not much) and didn't see this discussed -

I have 60k on a Mazda 6i (auto trans) - fluid never chged - looks a bit brown - I read on a Mazda forum that there can be issues with "flushing" old fluid - and that is, if the fluid is old, then a drain and fill is better. The poster (who otherwise seemed knowledeable) stated that the trans basically adjusts to the older fluid - and putting a newer (more slippery) fluid in could cause troubles.

Add to this - a friend of mine recently ask Midas about a trans flush (which was probably a mistake from the get-go) - and the Midas mgr says he never does flushes on a (in this case) Honda with fluid that's over 30k old (apparently same reason as poster above).

This all sounds nutts. Any truth to it?

Thanks!!

 

[bepperb]

Flushing, using a cooler line to completely drain and fill, and doing incremental drain and fills are three different things.

But yes, the first is ill advised and the second two are completely acceptable ways to do this. I really doubt you'd have a problem replacing it all at once via the cooler line method, especially at a relatively low mileage.

 

[ryland]

I always just drain and fill early and dont worry about the cooler line as that can get messy in my experiance.

 

[stranger706]

If you have a 6i, you must have the 2.3 then. I wonder if our cars share the same automatic tranny. Because on my 07 3s, there is a drain hole on the bottom of the trannsmission pan, just like the oil pan. Lots of Mazda3 guys just drain fluid out, and fill it up with new fluid, as opposed to the $150 dealer flush. I get 3.25 quarts out when I do this, which is every 10,000 miles. Keeps the fluid nice and fresh. I refill with Supertech Mercon V (less than $4/qt at Walmart), which is a tad thinner than Mazda MV fluid when cold. At operating temp its the same viscosity. It works great. Shifts are super smooth, and Mercon V is a very high quality ATF which lasts for a long time.

Let me know if you want more details.

 

[jcwit]

I have a KIA not a Maxda but with that said I do a drain and fill every other oil change with the recommended fluid. As stranger 706 says it keeps the fluid nice and fresh and isn't expensive, cheaper than a new tranny for sure.

One thing about KIA Rio's they don't have an easily accessible tranny filter.

 

[sunfire]

Originally Posted By: ericthepig
The poster (who otherwise seemed knowledeable) stated that the trans basically adjusts to the older fluid - and putting a newer (more slippery) fluid in could cause troubles.


Reset the car's ECU. Force the computer to relearn.

 

[Saturn_Fan]

I had to laugh at the too slippery comment if you add fresh fluid to older fluid (in this case 30K mile which is not old). Too funny the information out there.

Anyways, I do a drain and fill on my 08' Corolla. Four quarts comes out of the drain plug and is a breeze to do. Easier than changing the oil IMHO.

I plan on doing this every 15K during the life of the car. I do plan on dropping the pan and getting that screen cleaned out and the metal shavings cleaned.

 

[ionbeam22]

The deal is that replacing the ATF either by draning the pan, or by using the transmission pump is perfectly ok.

What is not ok is to "flush" the transmission with anything but ATF, as that can loosen up all sorts of [censored] and harm the various friction valves/materials in the tranny.

If you must "clean" the transmission, drop in a bottle of trans-tune from Seafoam and then change the fluid after running the car for about 30 minutes. Then refill with whatever is the current modern ATF for your engine.

Transmissions are expensive so it makes no sense to skip on using cheap transmission fluid.

 

[ericthepig]

Thanks for all the input! I would normally just do a drain/fill - which is easy and I've done many on my Sienna. But the worn looking fluid led me to look into the flush. There's a trans shop here that'll do a flush with dino for $130, or with Amsoil for about $190.

Another one of those brood issues.

 

[KrisZ]

I would drain and fill, ATF has a lot of detergents and replacing all of it at once may have a cleaning effect that is happening too fast, the old fluid is brown, so it is safe to assume the trans is dirty JMO

Honda only recommends drains & fills, so there must be some merit to flushes causing damamge.

 

[Trav]

The myths never seem to stop coming.
Oil never becomes less slippery,it may get contaminated,go through viscosity changes,wear its add pack out etc but less slippery?
The line off change (i wont call it flush) method is recommended in the factory service manual for my 06 Infiniti M35X.

If the pan has a drain plug drain the oil,drop the pan,clean it and replace the filter.
Fill with the approx the same amount as was drained and remove the return line.
Put a hose on the line into a old gallon bottle and have someone start the car.
Stop the engine when jug is almost full or if air bubbles appear,refill with one gallon or removed ammount.
Repeat until the fluid coming out looks the same as what's put in,it maybe a couple of quarts more than the total fill spec.

If no drain plug is present just do the line off,stop at the first gallon then remove the pan and do the filter,fill and continue with line off change.

No pan,just do line off change.

Reverse flushing isn't the same as a line off change,i would never do it to any transmission i service.The line off gets the old fluid out of the converter.Drain and fill is akin a 2 or 3 qt oil change on a 5 qt pan,the end result is diluted fluid,IMO better than nothing but not by much.

After doing literally hundreds of line off fluid changes on GM,Ford,Honda,Infiniti,Toyota,MB,BMW etc over the last 30 yrs i have never had any failure or even anything weird happen using this method.

I wouldn't put seafoam or anything else in a transmission.Pale oil,alcohol with a splash of zippo fluid and red dye isn't going to help anything.Lubguard red was good stuff for fortifying inadequate older formulations but today's oils are superior and basically needs nothing "extra".IMO you cant go wrong with a high quality fresh oil to keep the box working nicely.

 

[ericthepig]

Decided to save some money. Bought 7 qts of SuperTech ATF - then bought 3 qts M1 ATF at Napa (already had one qt on hand) - drained & filled with ST (3.25 qts), drove around a bit - drained & filled with ST again, drove around a while longer. Drained & filled with M1.

Will now drain & fill with M1 once in each of the next two summers - and then run that a few years.

The factory fill was in pretty rough shape at 60k. Should be in pretty good shape now.

 

[PT1]

Originally Posted By: Trav
The myths never seem to stop coming.
Oil never becomes less slippery,it may get contaminated,go through viscosity changes,wear its add pack out etc but less slippery?
The line off change (i wont call it flush) method is recommended in the factory service manual for my 06 Infiniti M35X.

If the pan has a drain plug drain the oil,drop the pan,clean it and replace the filter.
Fill with the approx the same amount as was drained and remove the return line.
Put a hose on the line into a old gallon bottle and have someone start the car.
Stop the engine when jug is almost full or if air bubbles appear,refill with one gallon or removed ammount.
Repeat until the fluid coming out looks the same as what's put in,it maybe a couple of quarts more than the total fill spec.

If no drain plug is present just do the line off,stop at the first gallon then remove the pan and do the filter,fill and continue with line off change.

No pan,just do line off change.

Reverse flushing isn't the same as a line off change,i would never do it to any transmission i service.The line off gets the old fluid out of the converter.Drain and fill is akin a 2 or 3 qt oil change on a 5 qt pan,the end result is diluted fluid,IMO better than nothing but not by much.

After doing literally hundreds of line off fluid changes on GM,Ford,Honda,Infiniti,Toyota,MB,BMW etc over the last 30 yrs i have never had any failure or even anything weird happen using this method.

I wouldn't put seafoam or anything else in a transmission.Pale oil,alcohol with a splash of zippo fluid and red dye isn't going to help anything.Lubguard red was good stuff for fortifying inadequate older formulations but today's oils are superior and basically needs nothing "extra".IMO you cant go wrong with a high quality fresh oil to keep the box working nicely.



+1 good advice here.

 

[doitmyself]

Originally Posted By: Trav
The myths never seem to stop coming.
Oil never becomes less slippery,it may get contaminated,go through viscosity changes,wear its add pack out etc but less slippery?


Hmmmmmm? I thought that one of the components of the ATF add pack were friction modifiers and that they affect the smoothness of the shifts. If they break down, "shudder" can be one result.

Is this not a change in "slipperyness"? Why do some transmission computers have to "relearn" or be reprogrammed when new (different friction) fluid is introduced?

Isn't friction and slippery somewhat the same? Isn't a change in friction properties more or less a change in how slippery a fluid is? Maybe the base oil doesn't change, but doesn't the ATF itself change regarding how slippery it is?

Anyone?

 

[Trav]

The OP spoke about new fluid being "more slippery".
The way i understand it(mind you this was from my teacher almost 40 yrs ago)its the degradation of the add pack,viscosity changes and contamination that cause the fluid to "wear out".I assume this includes the friction modifiers.
If the friction modifiers were worn out then i would guess the old fluid is actually slipperier then the new fluid.

Is it possible the friction modifiers are there to increase friction for the bands and clutch pack?

What i meant is if it were possible to strip all the additives out and return the old fluid to its original state then it would be just as slippery(although i don't know how you would measure this) as it was in the beginning.Maybe slippery isn't the correct term at all.

Higher viscosity also creates drag which is friction,is a higher viscosity oil less slippery than a thinner oil?I have no idea.
It would be nice to hear from the experts about this.

 

[unDummy]

Eric, there is no running anything for a few years. You should pick a drain/refill interval and stick with it, like once a year or every 10k or......

Don't believe anything heard by quick lube or hack mechanics.

 

[ericthepig]

unDummy, that does sound like a good plan. The ATF drain/fill on this Mazda is way easier than the oil change (cartridge filter).

 

[Gary Allan]

Friction modifiers in transmissions should not be confused with friction reducers. MolaKule has posted a good bit on this.

 

[ericthepig]

Question - after all my drain/fills - I somehow now have an ATF level that is about 3/4 inch above the full tic mark (the low/high tic marks are set for 69degC (this is written on the dipstick)). I chked the ATF while fully hot (Op. Temp) - it had been driven a while and had gone thru all the gears - and the check was done while it was running.

So, should I panic and go out and drain a bit of fluid right now ? (it's been driven about 20 miles since the chg) Or can I wait till it's convenient (next day or two) ?

 

[Trav]

No panic.After 20 miles its good and hot at this time of year.
It will be higher on the stick than normal,probably not 3/4 of an inch but a little.Wait until it cools down a little and recheck.

You could pick up a hand held vacum pump from your local parts store or HF and a longer piece of clear plastic tubing from home depot to pump a little out through the dipstick tube.