# Effects of NOT Changing Tranny Fluid.....



## fordy (Sep 13, 2003)

...............Since we have some certified mechanics on here and pretty smart shadetree(s) as well I thought I'd solicit some opinions , Was told by an old time mechanic friend that leaving tranny fluid UNchanged over the useful life , causes fluid too..."Cook" and simply coats all parts in tranny ! Then , say after 100k miles , a flush causes the caked , cooked fluid and parts too simply sluff off and gum up the works . Does anyone else agree with this ? , thanks , fordy:huh:


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## zant (Dec 1, 2005)

BS...change fluid every 20-30k and tranny will go 200-300k.....Does he also say NEVER change engine oil because it will cause dirt,fuel,etc to no longer hold engine together??...some "mechanics"are like leftist-what happened 100yrs ago must still happen today.


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## fordy (Sep 13, 2003)

zant said:


> BS...change fluid every 20-30k and tranny will go 200-300k.....Does he also say NEVER change engine oil because it will cause dirt,fuel,etc to no longer hold engine together??...some "mechanics"are like leftist-what happened 100yrs ago must still happen today.



...........He was simply telling what "would" happen , IF I didn't change the fluid on a regular basis . I guess I didn't phrase my statement correctly ! , thanks , fordy


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## zant (Dec 1, 2005)

No prob...it's just new(70-80's +)trannys are filled with better materials than old trannys-my grandfathers 48 Buick used a qt of oil every 600m from new and it was considered normal...sorry if I misinterpeted statement.


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## backwoodsman7 (Mar 22, 2007)

I've heard of problems caused by changing old ATF, but never actually seen it, and I've changed fluid in several older transmissions that were probably never changed before I got them.

A very good transmission guy once told me that 90-95% of his business came from people not servicing their transmissions. He recommended changing ATF every year.


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## Harry Chickpea (Dec 19, 2008)

Two top notch mechanics in Florida (one an ex-dealership shop supervisor and the other a transmission mechanic for many years) independently told me that the proper way to change tranny fluid is to drop the pan completely and do a thorough cleaning of the pan along with the change. "Cooking" is a good term. Cars that came into the south Florida market from the north made up the bulk of the tranny repair place's business. The combination of neglect and heat made them fail. I had a transmission fluid cooler put on the van prior to doing any trailer-pulling.


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## Guest (Apr 28, 2011)

There is an ongoing debate about this & I'm not convinced who is right . I believe if you have a low mileage vehicle & regularly change the fluid , that would be a good thing . I'm not so sure that if you have a high mileage vehicle that's never had the tranny fluid changed that it is a good idea to change it . 
My father-in-law had a transmission rebuilt & the re-builder told him not to change the fluid in a high mileage vehicle that had never had the fluid changed before . I know someone that bought a junkyard tranny & installed it in their pick-up truck . They drove it for a month or so & it worked fine . Changed the fluid & within a couple days the tranny messed up . Did changing the fluid cause it , I don't know but I wonder .
I have an old 85 Ranger that I have for farm use . The tranny will slip in reverse & I spent a lot of time on different forums researching transmission problems & repairs . I ran across many threads about whether or not to change the fluid . Most people agreed that if it was started at lower mileage & done regularly that was good . There was a lot of disagreement about changing higher mileage fluid .


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## blufford (Nov 23, 2004)

I've had several transmissions jam up after servicing. I've since left well enough alone and been okay.


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## foxtrapper (Dec 23, 2003)

I've never personally seen a case that I could absolutely and unequivocally attribute the transmission failure to changing old burned fluid. I have certainly seen failures I could directly attribute to the well burned fluid.

Were I to inherit a vehicle with nasty ATF fluid, I would flush it out. I would also be mentally budgeting for a transmission overhaul or replacement.

Personally, I change ATF fluid every few years. I do a thorough flushing, not simply dropping the pan. Does it work? Can't give you proof positive. I can say that I've had transmissions go many hundreds of thousands of miles without incident, including several that are known to fail early.


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## Beeman (Dec 29, 2002)

fordy said:


> ...............Since we have some certified mechanics on here and pretty smart shadetree(s) as well I thought I'd solicit some opinions , Was told by an old time mechanic friend that leaving tranny fluid UNchanged over the useful life , causes fluid too..."Cook" and simply coats all parts in tranny ! Then , say after 100k miles , a flush causes the caked , cooked fluid and parts too simply sluff off and gum up the works . Does anyone else agree with this ? , thanks , fordy:huh:


 The fluid doesn't "cook" unless the trans is being abused or failing. Is your friend referring to the useful life of the trans or the useful life of the fluid? Why change engine oil? An automatic transmission has friction clutches that have a fricytion material that wears. These clutches are brown and the worn friction dust turns the fluid brown. If you don't service the fluid there is more and more of this material flowing thru the trans. 
I can plan when I want to change my trans fluid, much cheaper and convenient then that unexpected trans failure.


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## unioncreek (Jun 18, 2002)

I wouldn't have a tranny flushed, have heard of too many failing right after they were flushed. On my 96 Dodge with the Cummins, yea the trannies were supposed to be crap. I got 230K out of the first one and the only reason it went south was the starter gear came off an went round and round knocking chunks out of the housing. I changed fluid every years and thats about 20K miles and adjusted the bands. I also added a temp gauge and never heated it up, but I didn't baby it either. 

Bobg


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## moocow (Jan 6, 2010)

Most people who have problems with there trans go and get it serviced, right? So they get their fluid changed and their trans goes out. They blame the fluid change, when they already had problems with it to begin with.

PREVENATIVE MAINTENACE is always the ticket.


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## OkieDavid (Jan 15, 2007)

I think more folks would service the tranny if;
1. The manufacturer would install a simple drain plug
2. The manufacturer would install an EXTERNAL filter.


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## fordy (Sep 13, 2003)

OkieDavid said:


> I think more folks would service the tranny if;
> 1. The manufacturer would install a simple drain plug
> 2. The manufacturer would install an EXTERNAL filter.


................The Allison on my 2003 8.1 dually has a simple screw on , external filter . $10 at any Allison dealer . , fordy


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## Allen W (Aug 2, 2008)

The transmission in the wifes 2009 caravan is sealed, doesn't even have a dipstick to check oil.


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## Bluecometk (Jun 20, 2009)

Subaru's have had Drain plugs on all of their Manual transmissions since 1969, Drain plugs on the Automatics since the mid 1970's and external filters on the autos since Midyear 1990. They also have changable filters in the valve body pickup tubes that are basically elephant traps for the big stuff. Subaruâs benefit from using Subaru HP trans fluid made by Idimitso. If the trans is displaying typical traits of delayed engagement or flaring between shifts the fluid change will actually improve the trans shifts and in most cases will stop/slow the bad characteristics. As a note you can only change about four quarts at a time even though the trans holds over ten quarts. So multiple changes will be ness to get the full benefits of the HP fluid.

just my opinions

Bluecometk


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## seagullplayer (Nov 6, 2008)

*I personally have had issues with high mileage changes causing problems.*

Both times I changed the transmission fluid that had never been changed I lost the transmission within a couple weeks. Both had well over 100K. No problems before the change. I stopped doing it.

I do believe that if you change as the manufacturer recommends you would be better off. But if you let it go too long, I would leave it be.


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## michiganfarmer (Oct 15, 2005)

I flush my own. I pull a tranny cooler line off the radiator. Run the engine till the fluid slows down. fill the tranny with new tranny fluid, run the engine. repeat till the fluid is clear. Drop the pan, change the filter, then top off the tranny. I bought the 97 f250 with 75000 miles on it, have flushed the tranny evry 30000 miles. I dot know if it helps or not. I have 175000 on the tranny now


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