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Old 02-10-2010, 05:57 PM
 
Location: Indianapolis
3,675 posts, read 8,247,796 times
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I own a 97 Toyota Corolla DX (1.8 L, automatic tranny) with 120K miles that I've posted about on here before.

Anyway, I asked my mechanic for an automatic transmission fluid/filter change which is due at this mileage (a flush has been done at 30K, 60K and 90K at the dealer), he tells me that I should not do anything like that to my transmission since the car is so old with so many miles. He says, the fluid is clean and a fluid change may cause problems down the road. He basically said not to change the fluid and just drive the car! He also said that new transmission fluid has alot of detergents in it and it may create some serious problems on an old car.

Has anyone ever heard of such a thing? I was shocked! I have always thought that the tranny fluid should be changed regularly. I am thinking about taking it somewhere else to have this done!! Basically, I want the tranny fluid drained, drop the pan, clean it, change or clean the screen/strainer/filter, put the pan back and put new fluid in it or flush it, whichever. By the way, this shop's been working on my cars for some time now, they do a great job and I completely trust them... well, until now! Any thoughts?
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Old 02-10-2010, 06:01 PM
 
404 posts, read 1,322,064 times
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i've read the same about older cars and the trans service

my volvo 740 has 139,000m and is due for one. but the fluid looks "acceptable" although dark, and recently my own mechanic (15 years) took a look at it and said "looks good don't worry about it"

so....some qualified answers would be appreciated by me, too

last service....about 20,000m ago
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Old 02-10-2010, 06:15 PM
 
Location: U.S.A.
3,306 posts, read 10,420,022 times
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Your mechanic is a moron. The only time the AT fluid should not be changed is if the same fluid has been run for high mileage. If you have been diligent in changing the fluid at those intervals then it will be fine to continue changing it out.

What happens when the same fluid is run in the transmission for high miles and is not maintained, all of the clutches and seals become acclimated to that old, seasoned fluid. If it is suddenly changed out then you induce a shock factor to those components and they begin to fail. Think of it like a blood transfusion, you just don't flush out someone's blood instantaneously.
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Old 02-10-2010, 06:21 PM
 
Location: Indianapolis
3,675 posts, read 8,247,796 times
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Quote:
Originally Posted by Lux Hauler View Post
Your mechanic is a moron. The only time the AT fluid should not be changed is if the same fluid has been run for high mileage. If you have been diligent in changing the fluid at those intervals then it will be fine to continue changing it out.

What happens when the same fluid is run in the transmission for high miles and is not maintained, all of the clutches and seals become acclimated to that old, seasoned fluid. If it is suddenly changed out then you induce a shock factor to those components and they begin to fail. Think of it like a blood transfusion, you just don't flush out someone's blood instantaneously.
That's exactly what I thought, that's why I was shocked!! The fluid in mine is pretty clean looking (nice pink color), it's been regularly flushed evey 30K miles. Last time, it was done 2 years ago when I first bought the car at 93K miles. So, should I take it somewhere else maybe even the dealer and get this done?
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Old 02-10-2010, 06:21 PM
 
6,368 posts, read 14,889,097 times
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As long as you've had it flushed as you say, there's no good reason not to continue to flush it when due.

If this was it's first service, then I'd say leave it alone.
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Old 02-10-2010, 06:25 PM
 
Location: So. of Rosarito, Baja, Mexico
6,806 posts, read 19,818,831 times
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The theory of a flush started back in the early 1950's with the intro of detergent in the oil. My dad had a gas station and shop and was talked into the new tech detergent oil by the oil company owner who was also a customer of my dad. The name McMillan ring a bell?

So dad did try the detergent oil in a customers car and it started to burn oil right away and cost my dad a ring job for free because of the detergent oil.

What happens is that over a period of time small corners (seals etc) are working well and then the flush will loosen up the seals and "VOLA" burning oil or slipping in the case of a Auto trans.

Bottom line is if there is no problem...don't create one. A simple fluid change and filter/screen in the tranny will suffice...NO flush.

A former retired mechanic and a son of a mechanic.

Steve
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Old 02-10-2010, 06:27 PM
 
Location: U.S.A.
3,306 posts, read 10,420,022 times
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Now... are you actually doing complete flushes or are you replacing filter and pan fluid only? It is unnecessary to complete flush out all of the fluid in those short intervals. You should only need to do filter and pan fluid each time. The transmission is a sealed system and the only particulate generated is from itself which is efficiently caught by the filter. If you wish to do entire flushes that's fine but it won't help you much in the long run.

Also, make sure Gus and Earl down at the local garage are using the proper ATF fluid for your vehicle and not some generic universal blend.
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Old 02-10-2010, 06:53 PM
 
13,687 posts, read 23,913,476 times
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Quote:
Originally Posted by ploopy View Post
i've read the same about older cars and the trans service

my volvo 740 has 139,000m and is due for one. but the fluid looks "acceptable" although dark, and recently my own mechanic (15 years) took a look at it and said "looks good don't worry about it"

so....some qualified answers would be appreciated by me, too

last service....about 20,000m ago
It looks good because it was serviced. The issue comes when tranny fluid burns and by then it's too late - it will start effecting your transmission components then.

A "flush" using your transmission oil pump is the safest way to go, not sure what AW tranny you have, possibly the AW30, but on my AW50 in my 850 I can drain the pan (around 4 quarts, or 1/3 of the tranny level) and that will slowly recondition the fluid. What you want is new fluid in there before the old fluid gets burnt. If you wait too long and change out all old fluid with new you *might* get into issues but in almost all AW trannies if your tranny is starting to mess up and you change the fluid you will be better off.
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Old 02-10-2010, 07:01 PM
 
Location: South Jersey
7,780 posts, read 19,590,638 times
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exactly. correct. Your mechanic is wrong


Quote:
Originally Posted by Lux Hauler View Post
Your mechanic is a moron. The only time the AT fluid should not be changed is if the same fluid has been run for high mileage. If you have been diligent in changing the fluid at those intervals then it will be fine to continue changing it out.

What happens when the same fluid is run in the transmission for high miles and is not maintained, all of the clutches and seals become acclimated to that old, seasoned fluid. If it is suddenly changed out then you induce a shock factor to those components and they begin to fail. Think of it like a blood transfusion, you just don't flush out someone's blood instantaneously.
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Old 02-10-2010, 07:03 PM
 
Location: Maryland
1,667 posts, read 8,768,743 times
Reputation: 1646
I've heard what Lux Hauler says. My oil change place always wants to do other work, like differential fluid, tranny fluid... I finally agreed to a transmission fluid change. The boss came out and said, with 150,000 miles on fluid, the fluid has become part of the engine and the parts are "acclimated" to it. He said that he's seen cars need a new tranny after the first high-mileage change.
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