# Transmission fluid: Change it, or leave it?



## clovis

I have a 1998 Chevy Monte Carlo with 138,000 miles on it. 

My dad gave me the car back in '03. 

The transmission fluid has never been changed. I thought that he had the TF changed at 60,000 miles, but I learned later that he did not. 

You can beat me up if you want, but I am asking that you be somewhat kind about it. I've had some health issues, and sometimes it has been difficult to keep up with family, work, and keeping a roof over our heads. 

I've read all over the internet "do not change ATF on a high mileage car if it has never been changed." I've heard that same advice before in real life.

But what I've found, most often, is that there is a small handful of people who _really know_ transmissions, and a whole bunch of people "who have heard" because their brother's neighbor had an aunt who had a second cousin that lived in Kentucky who owned a Toyota....

I tell ya, I'm not sure what to do. The tranny is shifting fine. Fluid is dirty, but isn't burnt. No metallic flakes in the fluid on the dipstick. 

A flush is totally out of the question, IMO.

I'm not sure whether to do a pan drop, change the filter and fill it back up, or try to find a pump and try to remove a quart through the dipstick tube each week, and slowly replace the fluid. The thought behind this method is that I would not be 'shocking' the transmission with 5 quarts of new ATF. 

I guess another option would be to unbolt the pan until it starts leaking, and let a quart or so drain out, and refill. Doing this periodically until I think all is okay, and then dropping the pan and completing a full fluid and filter change. Messy, for sure. Time consuming and expensive too. 

Do the Harbor Freight hand pumps work? Can you get ATF out of the dipstick tube?

Thoughts? Opinions?


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## nosqrls

If you are going to change fluid change the filter.


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## unregistered41671

IMO, I would leave it and just add fluid , if needed. I have heard of horror stories about people changing fluid on trannys that had fairly high mileage and shortly after adding fluid , had to rebuild or replace the transmission.


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## clovis

Yes, I would change the filter too.


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## Allen W

I know good and well that 90 silverado the boy is driving never had the trans oil changed, It had about 195,000 on it when it quit. Picked up a used transmission from the salvage yard and put in it and went on.


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## backwoodsman7

If you drop the pan and change the filter, you're really changing only half the fluid, because half is in the torque converter and won't drain out. I think the stories of transmissions dying after changing the fluid are old wives' tales -- I've done several and never had a problem -- but if you're worried about it, that might be a good in-between option. And you definitely want to change the filter anyway.

A very good transmission guy once told me transmission fluid should be changed yearly. He said 90% of his work is because people don't do that.


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## farminghandyman

from my experience on the newer transmissions, (front wheel drive stuff), basically from the mid 80's up, changing the fluid is importing to change the oil, I have had a few GM cars that the transmission craped out on about 150,000 most was do to oil not changed, 
the ones I have had proper maintainer on they have lasted much longer, CHANGE THE FILTER (many times it is the filter that is the cause, it starts to plug and causes a shortage of pressure and the transmission starts to slip and wear, ( not noticeable at first, but enough to shorten life), in time it will not be shifting correctly or not at all, 

by that time some times you can change the oil and filter and get some more miles out of it but usually by that time the insides of the transmission ( the clutches and bearings) are going or gone,

Change the oil religiously on the auto trans mission, 

on the old 70's units both ford and gm, they would take a lot more abuse than the modern units, 

many times the oil is fine, but auto transmission oil has a ton of additive in it to make it work correctly in the unit, and than tis what breaks down, 

when it turns dark (not burnt) most like it is very fine clutch dust in the oil, and other wear components.

many times when you take the pan off to change, you will find a 1/8 to 3/16" of sludge in the bottom of the pan, than is mostly clutch materials and bearings and oil breaking down.

My two cents


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## clovis

farminghandyman,

Do you think I should change it by doing a pan drop with a new filter @ 138,000 miles?


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## NC_hobbyfarmer

Once again this is just an I heard thing but it was to drop the pan, change the filter, remove the sludge if any and to filter the oil but re-use the old oil. Top off as needed with new fluid and go with it.


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## Caz

GM recommends a filter and fluid change at 100K but they don't recommend a flush. This is what I go by and recommend.


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## Allen W

Your at a point now with the transmission that in my opinion it won't matter a lot what you do, change or not change. I would drive it and keep in mind it could fail some where ahead and need replaced.


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## backwoodsman7

Keep in mind, manufacturers' recommendations are mostly concerned with keeping it going through the warranty period. Longevity after that is not in their best interest; the sooner it dies after the warranty expires, the more cars they sell. So if longevity is a priority for you, take that 100K with a grain of salt.


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## Guest

The never ending debate . The mechanic that rebuilt an automatic transmission for my father-in-law told him not to change fluid in a high mileage transmission that had never been changed . Having torn down an automatic transmission myself I found sludge built up in nooks & crannies in the valve body & other places .
If new fluid cut this sludge loose I could definitely see it causing problems . I think a new transmission would benefit from regular changes . If I was you I'd probably change the filter & strain & reuse the old fluid . Just my thoughts , no expert advice here .


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## coolrunnin

I have had pretty good luck doing a flush on high mileage trannies, but it sure isn't cheap.


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## wy_white_wolf

Most people only change the tranny fluid after they are experiencing shifting problems to try a cheap fix. Then they blame the transmission going out on the oil change. 

Change the fluid and filter before you have problems. Also double check that you are getting the proper oil for your transmission.

WWW


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## plowjockey

They say if you dont flush it half the old fluid stays in it anyway.

16 years and it still works without problems.

Fluid/ filter probably pushing $100 and money is tight.

Personally I'd just add fluid if/when needed and change when time/money permits.


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## Sawmill Jim

Wife's old car the head gaskets went second time in 200,000 miles ,transmission never touched :clap: Since the air don't work we just parked it and went and found her another car . :run:

Sometimes if it an't broke don't fix it comes to mind too. :awh:


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## fordy

clovis said:


> I have a 1998 Chevy Monte Carlo with 138,000 miles on it.
> 
> My dad gave me the car back in '03.
> 
> The transmission fluid has never been changed. I thought that he had the TF changed at 60,000 miles, but I learned later that he did not.
> 
> You can beat me up if you want, but I am asking that you be somewhat kind about it. I've had some health issues, and sometimes it has been difficult to keep up with family, work, and keeping a roof over our heads.
> 
> I've read all over the internet "do not change ATF on a high mileage car if it has never been changed." I've heard that same advice before in real life.
> 
> But what I've found, most often, is that there is a small handful of people who _really know_ transmissions, and a whole bunch of people "who have heard" because their brother's neighbor had an aunt who had a second cousin that lived in Kentucky who owned a Toyota....
> 
> I tell ya, I'm not sure what to do. The tranny is shifting fine. Fluid is dirty, but isn't burnt. No metallic flakes in the fluid on the dipstick.
> 
> A flush is totally out of the question, IMO.
> 
> I'm not sure whether to do a pan drop, change the filter and fill it back up, or try to find a pump and try to remove a quart through the dipstick tube each week, and slowly replace the fluid. The thought behind this method is that I would not be 'shocking' the transmission with 5 quarts of new ATF.
> 
> I guess another option would be to unbolt the pan until it starts leaking, and let a quart or so drain out, and refill. Doing this periodically until I think all is okay, and then dropping the pan and completing a full fluid and filter change. Messy, for sure. Time consuming and expensive too.
> 
> Do the Harbor Freight hand pumps work? Can you get ATF out of the dipstick tube?
> 
> Thoughts? Opinions?


 I use a set of steel drive on ramps , drain the pan (if possible) or remove it and let it drain . IF , you let it sit on the ramps for several days the fluid in the torque converter will drain out also , which is a good thing ! After Measuring the volume drained , I would add less than the volume drained , then drive it until the trany is warm and check the dip stick , adding small amounts in a multistep process to bring it up to full . 
Trany fluid expands as it gets hot , or atleast IT does when I serviced the Allison in my 2003 Chevy dually ! Without adding any additional volume , the fluid level on my dipstick kept increasing as the operating temps increased from ~170f up to 200f ! 
You might want to wait until spring to service the trany as it really won't get hot until the outside temps warm up. , fordy


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## Sawmill Jim

Fordy if that fluid don't get hot in ten miles i'll eat my hat :fussin:


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## fordy

Sawmill Jim said:


> Fordy if that fluid don't get hot in ten miles i'll eat my hat :fussin:


 .................If driven far enough it will , eventually warm up so I agree ! , fordy


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## chuckhole

Change the fluid and filter. Don't let it go any longer.

Unbolt 3/4 of the pan and let it tilt down to drain. Then loosen the remaining bolts to let it tilt slowly more and more so that you don't wind up with a shirt pocket full of tranny fluid. Clean the inside of the pan real good, replace the filter and see if there is a magnet in the bottom of the pan. There should be. Clean the fines off the magnet. Replace the pan gasket as well and DO NOT USE silicone or any other gasket sealer.

You will still have a quart or two left in the torque converter that will mix with the new stuff. Replace the same quantity that you drained out and start the engine. Check the dip stick with the engine in park at idle. It will have a cold line and a hot line on the dip stick. Fill to the cold line and warm up the engine/transmission and check it again. Do not overfill the transmission fluid. That is just as bad as underfilling it.

Personally, I would change the fluid/filter again in about 15-20K miles to get the "new dirty stuff" out. Be thankful that your tranny does not hold 12 qts of synthetic like my Allison 1000 does.


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## Sawmill Jim

fordy said:


> .................If driven far enough it will , eventually warm up so I agree ! , fordy


Yep if i remember right that car in the post has the built in transmission cooler in the radiator so when the motor temp comes up the trans. temp well too :runforhills: Or 5 miles a a 100 mph


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## farminghandyman

clovis said:


> farminghandyman,
> 
> Do you think I should change it by doing a pan drop with a new filter @ 138,000 miles?


 I would if it was mine.


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## farminghandyman

really the only way to get all the dirt out is to take apart and replace the torque converter, it works like a centrifugal filter, 

you could flush it and there will still be sludge and gunk on the out side edge of the converter, 

on some of the very first automatic tranys there was a drain plug on the converter and when you worked on it the converter could be taken apart for cleaning (think it was the old 4 speed hydromatic one had to separate the converter to remove as the front art was bolted to the crank like fly wheel on a standard, 
when they locked up in 4th they were direct dive like a standard, (something like with the locking converters of to day, on some units).


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## FCubSETN

Change the fluid and filter before you have problems. Also double check that you are getting the proper oil for your transmission.


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## zant

I change fluid and filter every 30k and use Lucas tranny stuff-99GMC-235,000-no problems...fluids are always cheaper than metal...as granddad taught me..


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## gohammergo

I don't know if this will work in your car, but my son just did this in his Ford Ranger. The line developed a small leak, and he didn't find out right away so he drove it low on fluid. Started not shifting right and the fluid was burned. When he got home he filled it up and drove it. Didn't shift good at all. So, he took the pan off and put a new filter and fluid in. Drove it for a few miles, and then did this:

Unhooked the transmission fluid line where it goes into the cooler. Started the truck and let it run until the fluid just stopped coming out. Put the line back on. Refilled it with new fluid and drove it to work all week. When the weekend came, he took the line off again when the truck was hot, started it up and let it idle until no more fluid came out and put another new filter in. Filled it up with new fluid and it has been shifting like new ever since! The fluid and filter are not real cheap, but much cheaper than a $1700.00 tranny rebuild!

Again, not saying this will work for you, but it did for him.


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