Old Dex And New ATF+4 Compatibility

[mikeymopar]

Getting the Charger back up and running after 30 years of sitting. Engine gone thru and running good. Moving on to the trans (A727 with a Stage 3 shift kit) and doing a quick filter and fluid change, I've read countless debates on types of trans fluid. Conclusion is keep it fresh and use whatever going by the plethora of comments. I've not seen a definitive answer on the mixing of old, straight up Dexron with ATF+4. Possible to mix the two types for a little while before doing another fluid change with more ATF+4? Or stick with something like a Castrol Transmax Dex/Merc (can get locally at a decent price) for compatibility sake with the old remaining fluid?

 

[YY1]

Best advice is:

Don't mix.

Pick one and keep using it. Might want to document it somewhere if using other than Mopar spec.

I use wal-mart's Supertech brand ATF+4. Easy to find and relatively cost effective.

 

[wagonman]

Drop the pan, change filter, drain convertor and flush or just blow out the cooler. Like YY1 said nothing wrong with Wallys ATF+4. Now I need to do mine.

 

[Darter6]

Let's hope your converter has a drain plug.If not what you stated in your first post,drain,fill, run it then change it again with ATF+4 you will be fine.
I will have to say I never had a problem with mixing Dextron,Dextron 2, and ATF+4. I even mixed Type F. Never had a problem.
This may be blasphemy to some,a quart of 30W non-detergent in the mix was a common practice with Torque Flights. Been doing that for 40 years or more.
My 1988 D350 Dodge has a mixture of all above for the last 12 years when I serviced it when I got it. A towing work horse.Still going strong.

 

[R413]

Dex-merc for the win here.
Always good to drain converter

 

[zyzzyx]

I just purchased two cases (12 Quarts) of Mopar ATF+4 at Menards for the best price I've seen! $4/Quart.

 

[440 PHIXX]

So... Are you not supposed to add Dex4 to what’s in the transmission? I just need to top it off.

 

[Darter6]

I will have to say I never had a problem with mixing Dextron,Dextron 2, and ATF+4.

Top it off. You will be fine.

 

[Cranky]

ATF+4 is syn.....I don't like to mix either.....

 

[440 PHIXX]

ATF+4 is syn.....I don't like to mix either.....

That’s what I was thinking about. All they had at NAPA was synthetic.