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Tranny fluid urban legend true or not?

Drago

Drago

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I was told if a high mileage vehicle with an automatic tranny had dark/burnt fluid but otherwise operating normally you shouldn't change the fluid but just keep it topped off. yes no maybe?
 
Pretty much what I have heard and it makes sense because there is a possibility of breaking loose solids with new high detergent fluid that could plug up the valve body and deteriorate hardened seals and make them fail.
 
Pretty much what I have been told being in the industry. Seen people come in with NASTY ones wanting a flush, see them again a few months later for a rebuild.
 
Myself and a couple friends learned it the hard way. Then later became friends with a guy that owned a huge trans shop. He said he spent years experiencing it and follows the same plan- once it has 100,000 miles then dont swap it. When low add a non detergent oil.

What happens is the detergent will scrub everything clean like it's supposed to. Then the crap washes through the system and will plug up the new filter rather quickly starving it.

The other thing it can do is the clutch packs have the material is worn down, but maintaining. The new detergent will wash away some of the older material quicker that was otherwise staying put. Then the slippy slip game starts.

How long will they last without trans service is th next question. At the fuel company fleet I worked at we did not service the trans in the pickups. Not one of the trucks that were not towing ever had trans problems. Many trucks would get 100,000 miles a year- not a typo. The trucks would be sold in the 350,000 mile range. One of the mechanics bought a 400,000 mile truck and put another 200,000 on it. Only the non detergent fluid was ever added.
 
How do you find non-detergent ATF?

I think the damage may have been done with old/never change ATF anyway.
Flushing is just an icing on the cake.
 
Well, i worked for a fuel/ oil company- so i just put in a material req to the warehouse. I havent googled detergent free atf...

I did learn that if someone did do new fluid after high miles, just drop in a new filter in a month. Depending on how plugged it was, do another filter in a month or two.
 
JMJNet said:
How do you find non-detergent ATF?

I think the damage may have been done with old/never change ATF anyway.
Flushing is just an icing on the cake.
Click to expand...
That's the way I've seen it.
If a flush/new fluid makes it slip, it was already time for a rebuild anyways.

Sent from my SAMSUNG-SM-G935A using Tapatalk
 
Friend of mine 40 years ago (he was in his late 20's) said only change a few quarts at a time as it could break off build up on the seals and definitely make it leak if you were to flush the whole system. Seemed plausible at the time and still might be the case...
 
the truck has 170k now and isn't slipping, I'm starting to throw money at it, just replace the AC compressor. thinking of selling it
 
Of course, that myth is also based, may be, by the different brand of cars/truck.

For example, GM probably have better trans compare to their competition like Ford and Chrysler.
For the Asian brand, Honda probably have the weakest transmission and it needs a special ATF.

This old truck will have a lot more money for fixing because it is "old".
That does not mean that the new ones are not.
 
I read somewhere for Ford, they have to change it at least once per year or 30K miles for the trans to last longer.
 
Depends on the tranny. Yes, some *need* fluid changes as early as 30K miles as the system does not get enough cooling and the fluid cooks. Even the owners manual spec's a short life.

Do not know much about the current generation of Fords and whether the engineers corrected / were allowed to correct the cooling issues of generations past.
 
I'll let you all know. I bought a 6.5TD with 4L80E and 140k. Trans fluid black on the stick and rag used to wipe the stick to check level, trans not slipping or shifting strangely. Dropped the pan, cleaned everything inside that spray cleaner could reach, new filter then: disconnected return line from cooler, put a hose on it into a drain pan, added new fluid at the top while the old fluid drained into the pan with the truck running and trans in neutral, when the fluid coming out of the hose changed from black to clear red, stopped and buttoned everything up. Trans is working beautifully, just like new. Don't know the history of the trans. Could the black be the metal and clutch material from a new, or reman, trans being broken in? No way to tell, but the pan and filter were cleaner than many I've done this to. Never have had a high mileage car or truck react badly to this treatment, but none of them were slipping or acting strange - because I usually drop pan and do new filter at major services on whatever vehicle I've ever had all the way back into the early '70's so I've never experienced a auto-trans failure in all these years and many, many vehicles. 70's were easier with the old Mopar 727 cuz they had a drain plug on the torque converter.
Filter and fluid every 30 - 50k, and yes Jay-theCPA, it is messy, but it is much cheaper than a new trans. Nice thing about my trans is there is a drain plug on it so the mess is minimal. I work my things hard, but I take care of them, which is why I don't have any sad stories to tell - only questions to find out others experiences and solutions I've found that worked. That's is what this post is being offered for, take it or leave it, but don't give me a bunch of personal junk if you disagree - see "Lift pumps".

I haven't towed my 4 ton mini excavator on my 1&3/4 ton trailer yet. I let you know how it goes.
 
Keep a watch on the fluid to see if it changes over the next 20K miles.


As comparison, I also bought the Burb around the 141K mark and the fluid was brown and heading toward black. Immediately changed the fluid with synthetic.

At ~160K the tranny still acted fine yet the fluid was black. Ended up having to completely re-build the thing as the only reusable parts were the case and pump.
 
Bought my '99 at 150K and change the fluid and filter every 15K. Currently at 212K. No slip. Doing fine.

Need to change door hinge pins and the install of the GMT 800 front brakes.
 
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