Dextron III / IV or Synthetic ATF

[Dan Fahey]

Corrected Post to Dexron...thanks!


Just bought another PerformaBuilt Trans from Alan Pickering.
Got their Heavy Duty 4L60E Truck version for the 94 Caprice Wagon.
Planning adding a 383 as the current engine has 250,000 miles.
This will complete the powertrain restoration.

Alan recommended any Dexron III or IV and Synthetic is ok.
Going to add a second cooler.

My question.
Does Synthetic AFT offer any advantage over Dexron?
Researching over the internet there is a lot of antidotal information.
Nothing is clear as to which is better for Towing.
Except Synthetic is a lot more expensive.

Looking at the Ounce of Prevention = Pound of Cure.
If it exists in this case.

Need some help.

Dan

[Myron Piatek]

I believe that quality synthetics offer an extra level of protection all-around, but mainly from their resistance to heat degradation. Heat is usually cited as the #1 contributor to transmission failures. I use the appropriate Amsoil synthetics in my race trans and pull it every 3-5 years years, not because of problems, but just as preventive maintenance. I bracket race and run association events as well as IHRA. My trans builder says to keep using/doing what I have been. I figure that trans brake and towing applications have more to gain from it than footbraking.

[ss3011]

Dextron is a copyright owned by GM . If the bottle of ATF says Dextron then it meets the GM specs for that Dextron fluid . They are tested and approved by GM . The later versions of Dextron which is now Dex6 , is able to service earlier versions of Dextron . So there are companies that make synthetic versions of Dextron , and they offer all the benefits of synthetic oils . Also the fluid that is specified for Allison automatics is called TransMax and is synthetic . It is a very high quality fluid that meets Dextron specs and is made by Castrol .

[Tim H]

It is actually DEXRON not DEXTRON as the original poster stated. Dextron is a veterinary medicine.Sorry just a pet peeve of mine after being a parts man for over 30 years !

[ss3011]

Darn auto correction feature !

[Rsmith38]

Synthetic VS conventional oil results in a 20 degree cooler temp in a street driven ENGINE (should be same in a trans? friction is friction).
My findings with oil temp guage on Jeep 4.0 engine.

[Dan Fahey]

Last year was very hot and towing up the Appalachian mountains was a real adventure.
I lost a transmission towing home from one race.
Only two miles from home.

Dexron ATF is sold under different brands.
Do these vendors make their own blends to meet Dexron specifications?

Is there an advantage of using a Dexron Synthetic over GM Dexron or one of its competitors?

Do any of the companies have a version of Dexron for heavy duty towing?

D

[FED 387]

Don't forget a huge trans cooler to plus the type and location so important too

[Mark Ugrich]

Dexron is licensed by G.M. Apparently to sell any dexron product the manufacturer must submit the blend and contents to G.M. for approval. From what I've read G.M. no longer monitors anything prior to dexron VI as dexron 6 supersedes all other dexron fluids.
I agree with Myron that the synthetics offer more protection against heat. The only draw back I've heard of is that in a high horsepower combination, the synthetic is so slick that it can allow the clutch plates to slip.If you plan to do a lot of towing I'd use the synthetic.

[SSGN]

Dexron 6 is a synthetic and is usually reasonably priced and works great in modern and older transmissions.