Dexron III or Dexron VI?

[OR VietVet]

Going to be doing the transmission fluid and filter service on my Tahoe. Has the deep pan. Owner's manual calls for Dexron III and is available. Is this recommended or use the Dexron VI? Thanks in advance for any info and recommendations.

 

[Fless]

I believe that GM (ACDelco) no longer licenses Dexron III (H). But Dexron VI (J) is backward compatible and, from what I read, has better shear qualities than Dexron III.

Note the license number in the graphic starts with "J..."

Could always ask @NickTransmissions if he has an opinion.

 

[Marky Dissod]

... Owner's manual calls for Dexron III ...

To oversimplify, it now calls for Dexron6.
(Even know a few people who've been using Dexron-HP in their 4L60E / 6L80E for over 30,000 miles, and prefer it over Dexron6.)

 

[OR VietVet]

Yea, my owner's manual calls for the Dexron III H and the label on that says replaces Dexron III and Dexron III H.

I can't contact @NickTransmissions because he blocked me. I bothered him too much with questions when I first bought that 2004 Silverado K2500HD with the 4L80E. I was asking questions about the solenoids replacements and asking about some steps for doing so and he got fed up with me and blocked me. I did just try to message him and I am still blocked. I meant nothing by anything I said and asked but I guess I got him on a bad day and I was just too much of a bother. All Good!

Dexron VI it is then.

 

[OR VietVet]

Did they say why they prefer it? What changed that made them prefer the Dexron III HP?

 

[Marky Dissod]

Did they say why they prefer it? What changed that made them prefer the Dexron-HP?

FYI, the 4L60E guy has a Buick RoadMaster LT1 (that I tuned when it was using Dex6; like your manual, it originally called for Dex3),
the 6L80E guy has a Suburban AND a Holden Caprice PPV, both are driven pretty hard compared to normal use cases.

They both reported better MpGs, smoother shifting at part throttle, and quicker shifts at WOT.
They changed from Dex6 to DexHP, ran DexHP for 30,000 miles, and stuck with DexHP.

 

[OR VietVet]

So, I should assume that since the transmission started with Dexron III HP and made it to this 176k miles, that if the same fluid is still available, I should stick with it. What if , when I first bought the Tahoe and I did a transmission fluid and filter service at 135k miles and used Dexron VI, like I think I did, gotta look at the paperwork, should I stick with Dex VI or stay with Dex III HP?

 

[NickTransmissions]

Yea, my owner's manual calls for the Dexron III H and the label on that says replaces Dexron III and Dexron III H.

I can't contact @NickTransmissions because he blocked me. I bothered him too much with questions when I first bought that 2004 Silverado K2500HD with the 4L80E. I was asking questions about the solenoids replacements and asking about some steps for doing so and he got fed up with me and blocked me. I did just try to message him and I am still blocked. I meant nothing by anything I said and asked but I guess I got him on a bad day and I was just too much of a bother. All Good!

Dexron VI it is then.

I didn’t block you, specifically.

I turned off my PMs as too many people were sending me messages asking questions that should be asked here on the forum. There is zero reason to send anyone PMs with tech questions as it’s completely redundant and defeats the purpose of having an open forum where everyone can learn/exchange information.

Dex Merc fluid is all you need for 4L60Es and 4L80Es.

 

[strutaeng]

Dex VI basically superceded Dex III in 2009 or something like that. I think there was a technical bulletin on it.

Dex VI should be available locally. I guess I've never run DexMerc, but that should works just as well as @NickTransmissions pointed out.

I can't even remember seeing Dex III on the shelves for the last 5-6 years?

 

[OR VietVet]

Dex VI basically superceded Dex III in 2009 or something like that. I think there was a technical bulletin on it.

Dex VI should be available locally. I guess I've never run DexMerc, but that should works just as well as @NickTransmissions pointed out.

I can't even remember seeing Dex III on the shelves for the last 5-6 years?

The Dex III was available at RA. They also have DEX VI, which I will be using. The money I save on the DEX VI, by ordering from RA, is eaten up by the shipping of heavy fluid. I do have a $140 RA Store Credit that I need to use but unsure if I want to use it for the deep pan Genuine GM filter kit and the fluid. Damage and possible fluid leakage worries me.

@NickTransmissions, it has been long enough ago, that I forgot that the message blocking was because of what you just said and not because of any perceived reason that I stated. Sorry.

 

[Marky Dissod]

So, I should assume that since the transmission started with Dexron III and made it to this 176k miles, that if the same fluid is still available, I should stick with it.

No, Dex6 is interchangeable with Dex3, feel free to use either, although I'd prefer Dex6 in any case where Dex3 is available for a 4Lxx or 6Lxx.

What if, when I first bought the Tahoe and I did a transmission fluid and filter service at 135k miles and used Dexron VI, like I think I did, gotta look at the paperwork,
should I stick with Dex VI or stay with Dex III HP?

Don't worry so much. Dex6 is basically a superior version of Dex3 (yes, I'm oversimplifying), feel free to use Dex6 in any automatic that used Dex3 in its past.

Dexron-HP is an even further refinement/improvement of Dexron6; although Dexron-HP is spec'd for 8L90s, I'll be adding it to my 4L60E at its next fluid change.
Those of you who don't like to take the kinds of chances I do, stick with Dexron6 for your 4Lxx & 6Lxx.

 

[NickTransmissions]

No, Dex6 is interchangeable with Dex3, feel free to use either, although I'd prefer Dex6 in any case where Dex3 is available for a 4Lxx or 6Lxx.

Don't worry so much. Dex6 is basically a superior version of Dex3 (yes, I'm oversimplifying), feel free to use Dex6 in any automatic that used Dex3 in its past.

Dexron-HP is an even further refinement/improvement of Dexron6; although Dexron-HP is spec'd for 8L90s, I'll be adding it to my 4L60E at its next fluid change.
Those of you who don't like to take the kinds of chances I do, stick with Dexron6 for your 4Lxx & 6Lxx.

Please let us know how you like the HP stuff in your 60E. I believe that fluid is ULV but otherwise have never had anyone provide first hand experience when retrofitting it to older units.

 

[OR VietVet]

I ended up buying Valvoline Dexron VI / Mercon LV. Said is recommended for use in Dexron II, Dexron III, Dexron VI and Mercon LV.

I am using the Genuine GM filter kit/includes gasket #24208576. I do have the stepped/deep pan.

Should be ok, correct? I will be doing the service in a day or two. Unless you say differently, of course.

 

[Marky Dissod]

I believe that fluid is ULV, but otherwise have never had anyone provide first hand experience when retrofitting it to older units.

My understanding:
10L80/10L90: GM DEXRON-ULV ATF (FoMoCo uses Motorcraft ULV-ATF, which must be similar, given that Ford's 10R80 is very similar to the 10L80)
8L90 / 8L80: GM DEXRON-HP
6L80 & older: DEXRON-VI if it's an automatic

Turns out the 4L60E guy and the 6L80E guy using DEXRON-HP in their 4L60E & 6L80E, are both mechanics, however neither owns the shop they work in.
Wonder what info got them to consider using Dex-HP in place of Dex6?

Please let us know how you like the HP stuff in your 60E.

Will definitely keep y'all posted ...

... ended up buying Valvoline Dexron VI / Mercon LV ... Should be ok, correct?

Yes.

 

[NickTransmissions]

My understanding:
10L80/10L90: GM DEXRON-ULV ATF (FoMoCo uses Motorcraft ULV-ATF, which must be similar, given that Ford's 10R80 is very similar to the 10L80)
8L90 / 8L80: GM DEXRON-HP
6L80 & older: DEXRON-VI if it's an automatic

Turns out the 4L60E guy and the 6L80E guy using DEXRON-HP in their 4L60E & 6L80E, are both mechanics, however neither owns the shop they work in.
Wonder what info got them to consider using Dex-HP in place of Dex6?

Will definitely keep y'all posted ...

Yes.

Ah, you’re correct. The 8 speed stuff is classed as “low viscosity”, not ultra low viscosity like the fluid for the 10-speeds.

Wondering now if the LV fluid intended for 8Ls is formulated the same as the Mercon LV intended for Ford six-speeds (6R80, 140, etc). If so, it should be perfectly fine to use in a GM six speed. If it’s perfectly fine in a GM six speed, it would be formulaically the same as Dex6, which of course, is backwards-compatible with all transmissions that took the previous standard, Dex-Marc/Dex3.

 

[OR VietVet]

Ok, well besides some of the specs lingo you used, that I did not understand. It seems that the Valvoline Dexron VI/Mercon LV, that I bought, will do just fine, correct. I do know my owner's manual does say Dexron III HP. But that is an original 2005 Tahoe owner's manual. All good then, correct?

 

[NickTransmissions]

Ok, well besides some of the specs lingo you used, that I did not understand. It seems that the Valvoline Dexron VI/Mercon LV, that I bought, will do just fine, correct. I do know my owner's manual does say Dexron III HP. But that is an original 2005 Tahoe owner's manual. All good then, correct?

Dex6 full synthetic or Dex/Merc (conventional) will work - brand is your choice.

 

[OR VietVet]

I do like Valvoline products. Plus, I did find the paperwork, from last service 40k milrs ago. Did use Dex VI then.

 

[Marky Dissod]

8 speed stuff is classed as “low viscosity”, not ultra low viscosity like the fluid for the 10-speeds.

I'd be tickled pink if I could somehow be sure, but my strong suspicions are as follows:
DEXRON-ULV is a refined / improved / higher quality DEXRON-HP ... DEXRON-HP is a refined / improved / higher quality DEXRON-VI.

Wondering now if the LV fluid intended for 8Ls is formulated the same as the Mercon LV intended for Ford six-speeds (6R80, 140, etc)?
If so, it should be perfectly fine to use in a GM six speed. If it’s perfectly fine in a GM six speed, it would be formulaically the same as Dex6, which of course,
is backwards-compatible with all transmissions that took the previous standard, Dex-Marc/Dex3.

Above chart is for LubeGard's 'Complete Full Synthetic ATF', which among a plethora of others, covers
Mobil's PURE SYNTHETIC IMPROVEMENT OF GM's DEXRON-HP, DEXRON-HP, & DEXRON-VI.

 

[the 18th letter]

I want to change the trans fluid in my 99 with the 4L60e but at 160k and no problems, I’m afraid of creating one due to many conflicting views on high mileage initial trans fluid changes.