Change atf or not?

[countryguy1717]

Hello,

 

I have a 2014 sierra with the 6l80. It's coming up on 120k miles, bought it with 40k and I don't believe the fluid was ever changed before. The fluid is relatively dark. I notice an audible noise when shifting into drive and a little slippage in lower gears. 

 

I was thinking of just pulling about 4 quarts from the dipstick tube and replacing with dex vi. Has anyone done this at such a high mileage, or am I better off just riding it out until the trans goes?

[rav3]

I agree with u. Pull 4 out & 4 new. Then do it again at next oil change

[Grumpy Bear]

2 hours ago, countryguy1717 said:

Hello,

 

I have a 2014 sierra with the 6l80. It's coming up on 120k miles, bought it with 40k and I don't believe the fluid was ever changed before. The fluid is relatively dark. I notice an audible noise when shifting into drive and a little slippage in lower gears. 

 

I was thinking of just pulling about 4 quarts from the dipstick tube and replacing with dex vi. Has anyone done this at such a high mileage, or am I better off just riding it out until the trans goes?

 

Changing fluid may reduce slippage. MAY. But what your asking is about the same as "Can I unburn toast"? 

 

If a 4 quart gives a noticeable improvement then continue this process until the fluid is red in a jar, not on the stick, it will take quite a few. If it doesn't help then "Goes" will be defined by how much damage you are willing to endure. It's already going.  

[countryguy1717]

For ref here is what the atf looks like. Doesn't have a horrible smell. Where do y'all get ac delco dexron vi? None of the auto parts carry it

 

[rav3]

Definitely needs changing should be reddish on a paper towel like that.

[TheRiver]

Suck a gallon of ATF from the dipstick tube..................and replace with fresh ATF!!!

 

For now................

[countryguy1717]

Well I pulled about a gallon out, gonna do it again after a little bit. Will keep anyone curious updated if I have any issues

[Grumpy Bear]

Did it make a difference in shift quality? 

 

What I dropped on the first dump and fill on the right. What I get every time afterward on the left. I keep it cool and I keep it changed. 190,000 miles trouble free. 6L80E. Over serviced? Maybe. But I haven't spent more on fluid than a rebuild cost.  

 

Edited September 13, 2025 by Grumpy Bear

[countryguy1717]

15 hours ago, Grumpy Bear said:

Did it make a difference in shift quality? 

 

What I dropped on the first dump and fill on the right. What I get every time afterward on the left. I keep it cool and I keep it changed. 190,000 miles trouble free. 6L80E. Over serviced? Maybe. But I haven't spent more on fluid than a rebuild cost.  

 

Only drove it a day, can't really say if it helped yet 

[countryguy1717]

On 9/12/2025 at 11:31 PM, Grumpy Bear said:

Did it make a difference in shift quality? 

 

What I dropped on the first dump and fill on the right. What I get every time afterward on the left. I keep it cool and I keep it changed. 190,000 miles trouble free. 6L80E. Over serviced? Maybe. But I haven't spent more on fluid than a rebuild cost.  

 

It may just be in my head, but I've noticed a smoother shift and less of the clunking going from p r d. I redid about a 100 miles later, the fluid is still dark, but I'll continue slowly until its red

[Z45]

Why is it owners are obsessed with changing oil sooner than even GM recommends but when it comes to the Automatic Transmission Fluid,  mostly ignored until problems arise?  Everything GM puts into these vehicles come from a low bid supplier. Not saying it’s no good but when you rely on a low bid product you have be aware the bidder is only going to supply what’s good enough to meet GM specification, no more, no less.  GM power-train warranty on gas engines is 70,000 miles or 5 yrs, after that it the owners problem.

[newdude]

3 hours ago, Z45 said:

Why is it owners are obsessed with changing oil sooner than even GM recommends but when it comes to the Automatic Transmission Fluid,  mostly ignored until problems arise?  Everything GM puts into these vehicles come from a low bid supplier. Not saying it’s no good but when you rely on a low bid product you have be aware the bidder is only going to supply what’s good enough to meet GM specification, no more, no less.  GM power-train warranty on gas engines is 70,000 miles or 5 yrs, after that it the owners problem.

 

 

 

 

Because the OEMs are obsessed with telling us NOT to.  No such thing as lifetime fluids.  You should have seen ATF in a 6 speed from 07-15 after maybe 30,000-40,000mi.  You'd be insane to keep running it beyond that.  

 

The severe service schedule for GM trucks is every 45,000mi for transmission.  90+% of vehicles just based on where they are located fall under severe service (extreme temperature swings during the year).  Factor in driving styles, habits, short trips, long trips, towing, heavy payloads, etc.

 

Also... its not 5year/70,000mi powertrain warranty.  All GM gas cars and trucks except for the 2.7 Turbomax are 5 year/60,000mi powertrain warranty since 2016.  The Turbomax for 2024-current has the 5 year/100,000mi powertrain warranty, same as the 3.0 and 6.6 Duramax.  

 

Shorter oil change intervals for engines, transmissions, differentials and transfer cases has worked perfectly fine for decades prior, no reason those same practices can't still be followed.  Especially engine oil changes.  VVT, AFM, turbocharging, low tension rings, tighter tolerances, all the MORE reason to change oil more frequently as long drains can increase deposit rates and carboning.  

Edited September 21, 2025 by newdude

[Grumpy Bear]

5 hours ago, countryguy1717 said:

It may just be in my head, but I've noticed a smoother shift and less of the clunking going from p r d. I redid about a 100 miles later, the fluid is still dark, but I'll continue slowly until its red

 

 

Friction package is being restored  Keep going. 

[countryguy1717]

Well 3 month update. Not really a discernable difference between the second and third pull in color. Again it may just be in my head, but I've noticed a smoother shifting after the first pull. I guess my takeaway is pulling from the tube and replacing little by little is peace of mind at best.

[rav3]

It will get better. The 6L80 holds approximately 12.2 to 12.4 quarts of ATF. Each 4 qt R&R will get more & more of the old fluid out BUT, it just takes time. The clutch material is what makes the fluid dark in color. Clutch material is a fine abrasive, sort of like 2000 grit paper, so you want to get as much out as possible. Also, heat is a killer to the additives in the ATF & shear degrades the Fluid. You want it to get back to clear red. Your transmission filter will not filter that small of particles out. It only gets the big stuff, so don't worry about it for now.

Here's a good video.