Can I use Dexron VI in a 700R4 transmission? I was at OReilleys today and the guy said it takes Dexron VI --- but as far as I know, it takes Dexron III, and Dexron III is what is in it now.

If I can use Dexron VI, can I blend it with the Dexron III that will be left in the transmission when I change the oil? Does it have any advantages to use it in a 700R4 over Dexron III?

What's a good transmission filter? He said they have Pioneer, but I've never heard about that brand.

According to GM, you can use it; backwards compatible. I'm not sure what chemistry compatibility issues might occur with any seals. GM would know better than I in this case.

But, for the cost of some brand name DEX VI, you could probably get some really good (former) DEX III based fluid. Allison created a spec (TES-389) to mimmic the old DEX III fluids. I know there are several approved, licensed TES-389 fluids that would work for a moderate amount of money. (Mobil's "ATF D/M" comes to mind).

Or, you could "upgrade" to one of many synthetic D/M based fluids.

Thanks!

I don't want to spend a fortune on transmission fluid, but I know from my own experience that a good one can make a noticeable difference. But which one is good and easily available, like in a parts store or at walmart? The fluid from Mobil maybe? --- It seems that "double fluids" that are both Dexron and Mercron are the most available, but I don't know if it's a good idea to use such a "double fluid". That they work for both specifications can mean that they aren't "perfect" for any of them.

The transmission was rebuilt two years ago. Perhaps the parts used won't have problems with Dexron VI or a synthetic fluid, but who knows ...

The whole "double fluid" issue you refer to is actually to your benefit.

Ford's "Mercon" and GM's "Dexron III" were so incredibly similar that they can easily be considered one fluid. Hence, the aftermarket's approach to "D/M" "Dex/Merc" "D3/Mrc" and so on. Techinically, neither "Dexron III" or "Mercon" are licesned any longer, but the chemistry lingers on, in the aftermarket. The upside to this duplistic approach is that the market can make one fluid to meet both specs. That helps keep costs down!

Allison created the TES-389 spec to assure performance standards that used to exist with the Dexron III criteria, and added some seal compatibility criteria, if I'm not mistaken. Crafty1 could perhaps expound, but I'm not far off the mark, if at all.

If you want a reasonable performing fluid for moderate money, the choose any of the Dex/Merc products available from a quality brand name you recognize. It will work very well in your older tranny. The upside to the TES-389 fluids are that you are truly getting a performance guarantee.

Cool, then I don't need to worry about the "double fluids". I'll just have to go see what's available, check the prices and look up about the TES-389 and then make a decision.

But how about the filter? AcDelco can be hard to find; perhaps NAPA has good ones?

The Napa Gold series are clones of the Wix brand name line; very good stuff. Many of us use them with no issues.

Thanks, I'll try to get one from NAPA. Now I only need to find the time to buy everything I need and then to do it :)