Used Dex 3 in a 6L80

[myork831]

So poor attention caused me to end up buying Dex/Merc ATF instead of the valvoline MaxLife that I initially wanted. Filled the pan and idled it to temp until I realized I bought Dex 3 instead. Transmission has 205k miles, how bad of a mess up was this? I was doing regular maintenance and it didn’t have any issues but I’m afraid with its age I can’t exactly afford to do a flush so I’m hoping to be able to run what I got. Thanks

 

[BrianF]

In my limited opinion, it will he fine..ish short term. Likely the only issue will be some shift weirdness due to viscosity differences. I would do another fluid exchange before too long as a safety precaution.

Even so, viscosity is not the end all be all. In my 2017 Ram 3500, the Aisin transmission calls for a 7 or so cSt ATF. I used Maxlife which meets the specs but is like Dex 6, a 5cSt fluid. 67,000km later and I still can't tell a difference.

 

[Mooseman]

I think the major difference between Dex III and VI is that Dex VI is synthetic. Viscosity is likely the same as it is backwards to Dex III. Will Dex III harm your 6L80? Maybe not short term but I wouldn't leave it in there for too long as the fluid could break down more quickly.