Dexron III or Dexron VI?

[OR VietVet]

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

I did some digging and at 135k miles on the Tahoe, had done the transmission service with Valvoline Max Life 773775 fluid.

Knowing that this has been in my Tahoe for 40k worry free miles, is there a choice you would make as to what to put in now, during this planned transmission fluid and filter service?

 

[OR VietVet]

@Marky Dissod and @strutaeng, please look at my latest post on this subject.

 

[Marky Dissod]

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.

So, your 4L60E has not had any ATF changes of any kind for 160,000 miles, with no adverse effects or noticeable symptoms?

You already know there's two ways to look at this:
1. Change ATF like a normal person: shut it off, drop the pan, clean it spiq & span, screw the pan back on with a new gasket, add as much Dex6 as you lost, off ya go.
2. Set aside funds, prepare to rebuild your 4L60E, or remove yours and reinstall a pre-rebuilt one when yours inevitably schidts itself

When I said there are two ways to go about this, what I meant was, whether or not you do 1, you damnt well better be doing 2 as we speak ...

 

[strutaeng]

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.

You should be okay. "Don't replace your old ATF on a high mileage transmission 'else it will start slipping because of the 'grit' on the old fluid" is an old-wives' tale. Should be a PSA.

Old fluid with excessive clutch material that's been neglected DESTROYS bearings, bushings, valve bores, etc. That clutch material floating around will NOT bond itself back to the clutches backing plate anyways. It only hurts!

I did some digging and at 135k miles on the Tahoe, had done the transmission service with Valvoline Max Life 773775 fluid.

Knowing that this has been in my Tahoe for 40k worry free miles, is there a choice you would make as to what to put in now, during this planned transmission fluid and filter service?

View attachment 480684

That fluid should be fine. Actually a little better. I may look for that one next time I service my transmission, actually.

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.

View attachment 480678

Yes, stepped pan was introduced in like 1997. The filter should have the little "feet" or dimples on the corners.

Are you going to replace the filter metal-clad seal that goes into the case? It's kinda of PIA to remove, especially with ATF dripping on your face. I'd leave it if you serviced the transmission before.

Otherwise thread a 1/2" black iron pipe nipple from the hardware store. A 6" works well. Give it moderate wiggle and it comes right out. That takes about 30 seconds. It's a slick trick I learned from Mountains Garage on YT.

 

[the 18th letter]

So, your 4L60E has not had any ATF changes of any kind for 160,000 miles, with no adverse effects or noticeable symptoms?

You already know there's two ways to look at this:
1. Change ATF like a normal person: shut it off, drop the pan, clean it spiq & span, screw the pan back on with a new gasket, add as much Dex6 as you lost, off ya go.
2. Set aside funds, prepare to rebuild your 4L60E, or remove yours and reinstall a pre-rebuilt one when yours inevitably schidts itself

When I said there are two ways to go about this, what I meant was, whether or not you do 1, you damnt well better be doing 2 as we speak ...

None. About a year ago I had a line leaking bad enough that the fluid got low. I was getting a hard shift in 2nd and 3rd after highway driving for a half hour or more. Fixed the line and topped off the fluid and she been right since. I don’t and have never towed anything besides another car short distances since I’ve had it. Owned it since 49k. It may have gotten a change when I first bought it now that I’m thinking about it. That would have been the only one if I did.

 

[OR VietVet]

Yea, unless @NickTransmissions tells me to stick with what I have now, I believe I am going to go to O'Reilly's and swap out the fluids for the Max Life.

 

[Marky Dissod]

... @ 135k miles on the Tahoe, had done the transmission service with Valvoline Max Life 773775 ATF.
Knowing that this has been in my Tahoe for 40k worry free miles, is there a choice you'd make as to what to put in now, during this planned ATF & filter service?
View attachment 480684

Used to think that Dexron6 is Dexron6 regardless of who makes it, meaning that using that or any other Dexron6 would make no difference.
Then I had another think, and I've learned just enough about Valvoline to SUSPECT that Valvoline may be slightly more trustworthy than 'average'.
IFF I were to want to use Dexron6, YES, I'd use Valvoline's Dexron6 without hesitation; might even use it before I used a different Dex6.

I'm in a distinct mood to try DEXRON-HP / 8L90 ATF. Since GM had a TSB about this ATF, I'll be using LubeGard's ATF, which is backwards-compatible with
Mobil's updated pure synthetic LV-HP ATF, which addresses GM's TSB for DEXRON-HP

&
DEXRON-VI, which is backwards compatible with all older GM ATFs.

 

[SpareParts]

What is Dexteon-HP?
Never seen it before.

 

[Marky Dissod]

What is Dexron-HP? Never seen it before.

GM's 8L90 ATF (also applies to most of its lesser 8-speeds).
It was the subject of a TSB, whose solution was to replace GM's Dexron-HP with Mobil1's 'Synthetic LV ATF HP'.

 

[OR VietVet]

GM's 8L90 ATF (also applies to most of its lesser 8-speeds).
It was the subject of a TSB, whose solution was to replace GM's Dexron-HP with Mobil1's 'Synthetic LV ATF HP'.

And you can bet that Mobil 1 paid for that TSB "shout out".

 

[Marky Dissod]

And you can bet that Mobil 1 paid for that TSB "shout out".

GM been pinching pennies far too hard for over 10 years now.
'Da blood's not coming from the pennies, you schmuckdiots, it's coming from your fingers.' - and we're paying for the bandages.