Synthetic Dex3 vs. Dex 6

[umungus1122]

In my truck at the moment I have Castrol Synthetic Dex3 from when it was licensed. I have more of it, but I was wondering if Dex6 would be smoother or offer better protection, as I have some of that here as well. Full size Chevy with 4l60e and a transmission fluid to air cooler.

 

[MonumentOiler]

GM says go for it. Everything I see shows DexVI to be a very good fluid.

Not sure if it will offer better protection or smoother shifts but new fluid will whether DexIII or DexVI.

 

[SteveSRT8]

I can tell you that we have converted our fleet over to Dex VI which includes a couple of Silverados with the 4L65E and I cannot tell any difference.

But I have read the spec and I strongly recommend this fluid in GM full size trucks!

 

[MonumentOiler]

DexVI is running strong in my 99 Toyota Camry with a Aisin trans spec'd for DexIII. But I still have less than 10k miles on the fluid.

 

[jstutz]

I personally have not had good results running valvoline dex 6 in my old GM transmissions. Both had over 175K on them when i switched them. One has run on M1 its entire life with 30K changes and the fluid always looks brand new during change. With the dex 6 it was brownish at about 20K. I also noticed my shifting getting softer. Maybe something else was the cause as on paper the dex6 looks compatible. I did three flushes with ST dex3 and it is shifting better and now at 8K, the fluid is still nice red color. My suburban actually shifts better with the dex 6 but like the blazer, it is turning brown. Im not sure what is going on because it still shifts like new and works fine but the fluid is changing colors. I will be flushing it back out with Dex 3 as well. I gave the other 2 quarts to my dad for his allison transmission that calls for dex 6. Im really bummed that this didnt work out as it cost me 75 dollars for the case of valvoline dex6 at napa. Please dont take this as if im bashing dex 6 because im not. Im just sharing my experience with it. Afterwards i got to thinking that i should have kept the two quarts that i gave my dad and used them as PS fluid or something.

 

[beast3300]

I have dex 6 valvoline syn in the regal. It is still bright red after about 10k. I didn't notice any upshift change. The downshifts are quicker though. Prevous I had M1 dex3 in there. I say use what u got and fill in the rest with dex6.

 

[onion]

Some people say that as long as the ATF doesn't smell burnt, then color means very little. I really don't know. But when I used DexVI, I had similar results- it started turning brownish after around 20k. Didn't seem to change how it shifted or anything.

My results with DexVI have been mixed. It worked fine in my old 4T60e in my '94 Corsica (until the transmission died at 182000 miles... I think it was unrelated to the fluid, but I reckon we'll never know). But my '01 Lumina did not shift properly with DexVI. It made the 1-2 full-throttle upshift much to soft... it would do this slip & grab thing. I did a full flush with Transynd (synthetic DexIII) and the problem went away. The full-throttle 1-2 upshift is still softer than I'd prefer, but it's 'normal' for a white-bread family sedan like this. And it no longer does the slip & grab thing.