Michael Dowd

Hello All.
I am going to change the transmission fluid in my 1990 convertible and have a question. When I went to get it the computer said that I can use dexron III or dexron VI. they had VI in stock and that is what I purchased. Read the label after I got home it indicates that this is synthetic. Is it OK to mix the two? I will be draining the pan but the torque converter and cooler will still have III in them.
Thank you for an insight you can provide.
Mike

davewhtt

You can mix syn with dex 3 no problem. I surprised there hasnt been 15 replies with 15 different suggestions as to what brand to use.

Silver96ce

You can use synthetics in your transmission. Dex VI is supposed to lower viscosity ("thinner") fluid than Dex III. But it is supposed to be backwards compatible and should work just fine for your trans.

You can also use Mobil1 synthetic which is a very good trans fluid and is Dex III compatible. Amazon has a 6 qt. case for a little cheaper with free shipping -


And you can also use Mag1 synthetic. I have used it in my '94 F150 and will probably use it in the vette. Plus the price is much cheaper than Mobil1 and it has gotten very good reviews on Amazon and elsewhere -


For even less money you can get Mag1 Dex VI compatible synthetic -


All three are very good and should work just fine in your trans.

Vetterin

Dexron VI is just a synthetic blend fluid which is basically the same thing you would end up with if mixed full synthetic fluid with your Dexron III.

five7kid

Not exactly. Dexron VI is an updated ATF spec for GM vehicles. There are several changes made from Dexron III, including required viscosity and shear stability - two things that make using a synthetic base a good way to meet the requirements. As stated, it is backwards-compatible with Dexron III, and mixing the two isn't a problem.

Dexron III is no longer licensed. It may still be available from various suppliers, but you're basically on your own now.

vert vette virgin

So how effective is the filter in our AT' s? Is it vitally important to drop pan or is just a fluid change okay. The type quick change places do?

five7kid

Probably not a good idea to use quick change places as your model...

You might get away with it, but, really, is it worth saving $20 to risk $2000?

BOOT77

Just did my fluid, filter and pan a few weeks ago and used VI, you can change most the fluid. I bought about 7' of clear line at my local hardware store and used a gallon jug. Couple other notes are I shut it off when I saw air in the line at half the jug and if you have to walk away while your doing it the fluid may syphon(I came back to a full jug when I shut it off art half). I was putting a extra cooler on so I had to unhook the correct line anyway. Pan torque is 12 ft-lb


Good directions here post #6 from 383vette

http://forums.corvetteforum.com/c4-t...d-at-home.html

What line is what post #2

http://forums.corvetteforum.com/c4-t...es-in-out.html

Michael Dowd

I thought that I should be OK but the input from all of you make me feel better.
Have a great weekend.
Mike