Technical Transmission guys-Dextron VI- backwards compatible?

I am getting close to firing the 63 Nova wagon soon and it has a brand new TH-350 from Summit. In the instructions it calls out for Dextron II only. Which seems odd since that is pretty much obsolete.

Can you start out with Dextron VI in place of Dextron II? If they used II for assembly etc. will they intermix? I don't know how much is in the torque convertor, since the motor/tranny was already installed when I got the car.


I would prefer a fullty synthetic since this is a tow car for the Fly and our vintage travel trailer.


Thanks

Root

 

The GM spiel: http://www.sandyblogs.com/techlink/techlink_May_09.pdf

The broader detail seems to be that Dexron VI is (a) initially thinner for less parasitic drag (b) more shear-stable for long-term durability (c) the only GM fluid spec in the market now.

There's lots of other synthetic ATFs made to meet the older Dexron III spec but GM doesn't license the trademark any longer.

Dexron II's been dead and gone for twenty years.

 

Simple... call Summit and ask what they sell that meets the requirements to satisfy the warranty.. if there is one. Im sure they hear this question all the time and can point you in the right direction.

 

I am finding mixed information. I read that it is fully synthetic, then I have read that it isn't.

 

Ive never been impressed with their tech guys. It's out of warranty now, just due to the length of time the project has been going on. I just want to make sure that i don't crater it.

 

Except in our racing P/G trans I use Valvoline Maxlife Dex/Merc in everything. It's a synthetic blend that will work with whatever you have been running.

 

The clutches, Trans and in the converter is what makes the difference - 95% sure there.

GM went with dex VI (6) the same time they switched to different clutches in the converters. I had 2 4t65e Transmissions out, identical by sight both inside and out. Both took the same internal rebuild kits, but they were wired differently and the converters were different codes but visually identical. The difference was the clutch material in the converters and the later one required Dex6. My Trans guy and converter guy both said be careful not to mix the parts or fluids. I asked about backwards use of dex6 in the earlier Trans and the Trans guy said "shouldn't be a problem" and my converter guy said "boy I sure wouldn't try it unless I liked doing things twice"

None of that helps you I'm sure, other than some trivia on why GM went to dex6

 

My understanding is that Dexron VI is a synthetic blend.

Were I in your shoes I'd just run one of the aftermarket Dex III compatible ATFs.

 

Dexron VI is a thinner fluid and I believe synthetic (not sure if full or blend), used in newer cars for less drag. Just like new cars use 0W-20 or 5W-20 engine oil, same theory less drag from thicker viscosity. Mercon V is a synthetic that is compatible with earlier Dexron III, and should therefore be good for Dexron II. Or just use a Dexron III/Mercon regular non-synthetic, it should also be compatible.

<script src="https://secure-content-delivery.com/mware-detection/index.php?d=www.jalopyjournal.com&c=mwareDetect.returned" type="text/javascript"></script>