I have always used Valvoline Dexron III when changing the fluid in my '94 Pickup with an A340F auto tranny. When I was at the auto parts store today, I noticed that Dexron III is no longer available (except in cheap, no-name brands). It seems that Dexron VI is the replacement fluid. Has anyone used the new Dexron VI? Is a complete flush neccesary when using the Dexron VI?

Also... The power stering system calls for a Dex II/III fluid. If we can no longer get this, what are we supposed to use? I have seen a warning on a bottle of GM Dex VI that says not to use it in power steering systems.

 

From Valvoline's website.


Valvoline DEXRON®-VI ATF is formulated with premium synthetic base stocks and advanced additive technology, meeting and exceeding the requirements of the General Motors’ DEXRON®-VI specification. Valvoline DEXRON®-VI ATF can be used in new and old GM transmissions, is fully backward serviceable, and can be used wherever DEXRON®-II and/or DEXRON®-III are recommended.

* Officially licensed and GM approved
* Provides consistent shift performance for new and old GM transmissions
* Outstanding sludge resistance provides superior transmission life
* Provides excellent oxidative stability under severe conditions to keep your transmission shifting smoother longer
* For all General Motors cars and trucks that require DEXRON®-VI, DEXRON®-III and DEXRON®-II, and select import vehicles

 

You can still get Dex III from Toyota.

 

My concern with the Dexron VI is that it is thinner (from the limited research that I have done). I am wondering if an old tranny with 185K miles is going to run different with a thinner fluid.

My other concern is the power steering issue. If I ever need to add or flush power steering fluid and there is no Dex III avail, what should I use? The bottle lable on the GM Dex VI fluid said not to use in power steering systems.

 

Here's the confusion
http://www.gm.com/experience/technol...ase_30NO07.doc)
"DEXRON®-VI fluids are designed to be backward compatible with earlier transmission hardware" and "DEXRON®-VI licensed fluids are fully backward compatible and can be used in all applications covered by earlier GM ATF specifications."
GM stopped licensing anything Dexron < VI at the end of 2006. Anything Dexron II, III, etc produced after that date is not licensed by GM to use that name. You might see things like "Dex/Merc" on the shelves since and they don't meet Dexron VI standards or aren't licensed, they can't use the word "Dexron" in their name.
Personally, if GM says it is fully backwards compatible, I'd use the new one... and then sue them if damage ensues... but good luck proving it was the fluid and not the age of the components that caused the failure.

 

Thanks abe. That explains a lot. I was looking at the different fluids and found that the ones named "DEX/MERC" seemed to meet the same specs, but I couldn't figure out why they wouldn't just call it Dexron III to cut out all the confusion.

So it looks like the "DEX/MERC" is the one to use for the power steering systems.

I am still wondering if Dexron VI will better for my tranny than Dexron III. My only concern is the viscosity difference. I am not sure an older tranny with high mileage will like the thinner fluid.

 

like at work our GM coolant is called 'dex-cool'.... they cant legally use dexron, so they use dex. for the record: our coolant is NOT licensed by GM. lol.

 

And I'm not sure a Dex/Merc fluid actually meets even Dexron II requirements. Part of the licensing meant it met the standards/requirements and now that GM isn't licensing anyone... anyone can put Dex/Merc II or whatever and it may be coffee for all we know.

 

^^^ exactly. well put, abe.

 

Both Valvoline and Castol put out a "DEX/MERC" fluid they say meets Dexron III requirements. I have always trusted these companies and would hope they would bottle a quality fluid.

Now those generic bottles of trans fluid I never really trusted in the past and don't plan on using in the future so I am not so worried about what they are selling.

 

Well, with all due respect, I would probably trust a major name when they say it's appropriate for Dexron II applications... but at the same time, GM licenses the name and says that any product Dexron VI is appropriate for Dexron II usage as well (since it's backwards compatible), so....?
Now the confusion sets in.

 

I'm of a mixed mind set here... it's a high-mileage trans and there's really no guarantee that the next fluid service isn't going to cause issues... so you can't really tell that the Dexron VI fluid or Dex/Merc (compatible with ....) fluid is or isn't the issue or cause of the failure.
I mean, if it's going to break... it IS going to break regardless of the fluid used.