# To change trans fluid or not to change trans fluid?



## mkwl

Okay- I'm torn. My truck, a 2003 GMC Sierra 2500HD 6.0L/4L85E trans has 54,700 miles on it- it's due for a trans fluid change. Now, I bought the truck used with 39,000 miles on it- the truck was used as a plow truck- I'm not sure how the guy drove it, or if he ever changed the fluid. The fluid is red, and appears to be okay. My question is, should I mess with having the fluid changed and risk stirring up problems or leave it alone and just keep an eye on the level? The trans doesn't slip at all- did great plowing all winter- never got above 180* plowing (was usually around 170*). I'm worried that I'll have it change, stir up some crud that developed in there, and damage the trans that is doing fine right now. So, to change it, or leave it alone?

And if to change, just to drop the pan and change the fluid that drains and the filter, or to drop the pan, change filter and powerflush it and change the fluid?

Thanks,
Matt


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## 06HD BOSS

very good question. something i have thought about before too.


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## ABES

drop the pan and change the filter/fluid but DO NOT have it flushed, thats what stirs up all the debris in the transmission.


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## GL&M

ABES;563198 said:


> drop the pan and change the filter/fluid but DO NOT have it flushed, thats what stirs up all the debris in the transmission.


I agree. Never had a problem just changing the filter and the fluid. Once I had one power flushed and it wasn't the same afterwards.


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## B&B

If you do a search here you'll find a rather long thread from last year discussing this very subject...

But in a nut shell you want to change it NOW while the fluid is still relativity good...not after its broken down and turned to a brown color. This will keep and crud/varnish from forming in the first place.

And DO NOT power flush it. The 4L80E's don't take kindly to a power flush so do yourself a favor and dont have it done, just drop the pan and changing the fluid & filter is more than sufficient if you do it when you should.

How many of you guys are aware that GM (or most OEM manufactures for that matter) _*DOES NOT *_recommend a power flush on* ANY *of their transmissions for *ANY* reason?


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## 06HD BOSS

B&B;563219 said:


> How many of you guys are aware that GM (or most OEM manufactures for that matter) _*DOES NOT *_recommend a power flush on* ANY *of their transmissions for *ANY* reason?


i am now. thanks B&B. just money hungry dealers


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## mkwl

Okay- I have my truck scheduled to go in to have the fluid changed and filter changed- no power flushing! So I should not expect anything bad to come from changing the fluid this way, right?


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## Camden

Keep your fluid changed and don't think twice about it. You want to keep that fluid fresh so that you NEVER have trouble...it's called preventative maintenance. Spend a little now to save a lot later!


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## B&B

mkwl;564130 said:


> Okay- I have my truck scheduled to go in to have the fluid changed and filter changed- no power flushing! So I should not expect anything bad to come from changing the fluid this way, right?


Correct. A transmission is no different than an engine. Fluid and filter has a life expectancy and you want to change it before its life expectancy is up...simple as that.


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## gkm

thanks B&B you are a wealth of knowedge


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## Zodiac

I have to disagree with a lot of people here.

I used to own a quick lube business in town here.

I made good money from transmission fluid changes. And I've done over 200 of them on any possible make or model, with a few exceptions. 

I've never had one problem. I do my Suburban with a 4L60E transmission every 12,000 miles (I still own the machine), and I bought it with almost 90,000 on the odo. Never one transmission problem.

My plow truck has 160,000 on it, and I do that before every winter, and never one problem.

I've done lots and LOTS of 4L80Es, not one problem.


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## Zodiac

B&B;563219 said:


> How many of you guys are aware that GM (or most OEM manufactures for that matter) _*DOES NOT *_recommend a power flush on* ANY *of their transmissions for *ANY* reason?


B&B, I have to disagree with you. If you look through any model of GM truck, it recommends it be done every 12,000 miles (about once a year).

Allison does not recommend you do anything other than change the spin on filter on their 1000/2000 series transmissions, and even then, it's because the internal filter is basically a rock catcher.


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## B&B

Zodiac;564397 said:


> B&B, I have to disagree with you. If you look through any model of GM truck, it recommends it be done every 12,000 miles (about once a year).


I'm talking *FLUSH *not fluid & filter changes.GM does NOT recommend or endorse FLUSHES.



Zodiac;564397 said:


> Allison does not recommend you do anything other than change the spin on filter on their 1000/2000 series transmissions, and even then, it's because the internal filter is basically a rock catcher.


They do recommend changing the fluid as well at regular intervals depending on the severity schedule.

And your partially correct on the Allison filters. The internal filter has enough capacity to last the life of the trans while filtering out the larger micron debris...and the spin on is actually a secondary bypass type filter that filters to a much smaller micron rating. Which of course necessitates more often change intervals.


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## Zodiac

B&B;564400 said:


> I'm talking *FLUSH *not fluid & filter changes.GM does NOT recommend FLUSHES.
> 
> They do recommend changing the fluid as well.
> 
> And your partially correct on the filters. The internal filter has enough capacity to last the life of the trans while filtering out the larger micron debris...and the spin on is actually a secondary bypass type filter that filters to a much smaller micron. Which of course necessitates more often change intervals.


I take back the first comment I made, the manuals say nothing about flushes. Although I've never had a problem.

When I bought my Suburban, I got all the records with it, and nothing had been done with the transmission (INCLUDING FILTER). I changed that once, when I got the truck, about 20,000 miles ago.


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## mkwl

Got the fluid and filter changed on Friday- so far so good! Guy in the trans shop said to change it at least 1x per year if plowing- trans was in good shape- fluid wasn't too bad and no huge chunks of anything were in the pan- ready for another plowing season!


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## B&B

Good deal...take care of it and it'll take care of you when you need it the most> At least that's what we all wanna believe. 

Once a year F&F changes on a plow truck is a wise...but very small investment that can pay good dividends thoughout the life cylce of the truck.


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## Niteman9

What is a power flush? As I understand the process the cooling lines are removed at the cooler and the old oil is captured and new oil is returned to the transmission. I don't think the oil is pressurized any more than normal operation. I know on my 2002 powerstroke when I drain the pan I get about 7 quarts of oil. The capacity of the trans is 23 or 24 quarts. Therefore draining the pan only changes less than 1/3 of the oil. The rest of the oil is in the cooler and torque converter I guess. But I may be wrong. Who knows.


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## B&B

The problems that can stem from a power flush is that the fluid is pumped *backward* through the hydraulic systems and valves..and often times the fluid is agitated at the same time. This practice can stir up alot of debris (especially in a previously neglected trans) that wouldn't ordinarily create a problem. And the problem is compounded even more if the pan isn't dropped and the filter changed afterwards.

Late model transmissions are very contamination sensitive due to their complex circuits and electronics. Doesn't take much debris to foul one up.


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## JK828

I need to have my trans fluid changed, and after reading this I contacted my Chevy dealer. They said they do not flush the transmission but they evacuate the fluid. Is this actually different than flushing? Also, they said they do not change the filter only the fluid. is this good or bad?


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## B&B

JK828;565067 said:


> I need to have my trans fluid changed, and after reading this I contacted my Chevy dealer. They said they do not flush the transmission but they evacuate the fluid. Is this actually different than flushing? Also, they said they do not change the filter only the fluid. is this good or bad?


Evacuating is just the dealers lazy way out of doing it properly but still charging you for it. If you don't drop the pan for clean-out, and replace the filter...there's no point in changing the fluid. 

Evacuating your engine oil and not changing the filter would be about the same thing. Don't allow them to take your money.


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## Niteman9

Ok I drop the pan and replace the filter and change 7 quarts of oil. How do I change the remaining 4 gallons of oil?


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## B&B

Niteman9;565970 said:


> Ok I drop the pan and replace the filter and change 7 quarts of oil. How do I change the remaining 4 gallons of oil?


 4 gallons?... what kind of trans you runnin'?


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## Niteman9

I have a 2002 Ford F-350 and the owners manual says it has 24 quart capacity.


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## B&B

Not doubting your owners manual but even with the biggest factory cooler these trucks were equipped with ( larger 26 plate cooler, normal was 20 plate) I've never put more than 17 qts in a freshly rebuilt (dry) 4R100 with a new converter.

But regardless if you want to get as much fluid out as you can, which most will be in the converter... drop the pan, change the filter and let it drain with the pan off for a few hours to get as much out of the converter initially as possible. Then seal it back up and pour 6 qts in the pan. Then remove the return line from the cooler, add a short piece of hose to it and place it in a 5 gal bucket. Now with a helper: start the truck and immediately begin pouring fresh fluid in. The trans will pump the old fluid from the converter in about 20-30 seconds but with you pouring the new fluid in it wont run dry. After pouring appox 5 or 6 qts in turn the truck off, reconnect the cooler line and continue to refill to the correct level. Sounds more time consuming than it is and by doing it this way your not agitating the fluid or backflushing as many power flush type machines do...ensuring a complete fluid change without causing issues.


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