Dex 3 or Dex 6

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Nov 10, 2016
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145
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Missouri
My brother has a Hughs built 4L60E going behind a 580 hp LS3 in a 67 Camaro. The question is what type of trans fluid to install in it. Someone told him Dex 3, but i would use Dex 6 just because i believe it's a much better fluid. What do you guys think ?
 
Go with what Hughs recommends. 4L60E is an older trans and would probably do well with DEX III. It's cheap enough to change often. And, millions of cars have gone millions of miles using DEX III. If DEX 6 is recommended by them, then use that.
 
He does not know what they recommend until he can call them on monday. I run the Mobil Dex 3 synthetic in my 99 suburban but next change i think i will go to Dex 6. Just wondering what is a better fluid.
 
DEXRON VI is a better fluid than III day long. Better oxidation resistance and better shear stability. It starts off with a slightly lower viscosity but retains it much better than the old DEXRON III (which is an obsolete license).

There’s nothing wrong with the Mobil 1 product though except for the price. Maxlife ATF is a good alternative.
 
He does not know what they recommend until he can call them on monday. I run the Mobil Dex 3 synthetic in my 99 suburban but next change i think i will go to Dex 6. Just wondering what is a better fluid.
My 2005 Silverado had 3 it's entire life-I tried 6@240K miles and the tranny did work as well as it did with 3 (seemed to 'ease' into high gear, etc). I put 3 back in and it returned to it's original performance.
 
I don't believe 668 is compatible in that application, that's why TES-295/TES-468 fluid will continue to be available.
I went and found the Castrol spec sheet for the 668 version of TranSynd and it says it's fully backwards compatible with 295 but not for 468, so it would be great for Dexron III applications.
 
With Dex VI you'll have the wrong viscosity fluid in that 4L60E for anywhere from 15K-30K miles. If you want a 7.4 cSt Dex III that
holds up longer go with M1 ATF, DW4 ATF, Amsoil ATF, and a host other full synthetics that don't shear much.

5.8 vs 7.4 cSt starting viscosity is not insignificant. If the 4L60E has been rebuilt with modern parts, the Dex VI is probably fine.
 
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He just bought the Dex 6 today.
Rest assured.

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