A question about automatic transmission fluid

[bronze turbine]

In my '68 Chrysler I've been using the so-called "universal" "multi-use" transmission fluid, which I believe is basically equivalent to the Dexron III we used to use back in the day. I've been told that the latest spec Mopar fluid (ATF +4, I think) isn't backwards compatible and shouldn't be mixed with the old Dexron fluid. BUT, my question is, what about the new Dexron 6? That's supposed to be backwards compatible all the way to the original Dexron. Is anyone using that? Should I just stick with the "universal"?

 

[MONC440]

I always try to stick with whatever I have been using since the last rebuild. In a pinch anything is better than running it low. I would keep to the Dex III if that's what you have been using.

 

[413]

I would not mix synthetic and Dino fluids.
I would not use synthetic in a used transmission.

 

[1970FuryConv]

I would stay with Dexron 3.

I have used synthetic Valvoline ATF+4 in 1990 W150, 2009 Nitro, 2011 Nitro, trans oil changes every 60000 miles. Synthetic improved performance in all 3 vehicles.

 

[CBODY67]

Dex VI is backwards compatible to the first GM automatic trans, like in 1949, replacing Dexron-family and Type A fluids, per GM literature. Initially, Dex VI was a semi-syn fluid, but now might be full-syn, haven't verified that lately, though. I do know that GM is specing some different non-Dex VI fluids for the 8+ speed automatics, which are expensive.

ACDelco lists an atf that is, basically, Dex III fluid. If the multi-use atf you are using, on the back of the container, reads like it is aligned with Dexron-type fluids and the vehicles that used it, then it should be fine. Some multi-use fluids are aligned with Honda and other import brands, by observation. So reading the container is important.

Enjoy!
CBODY67

 

[fury fan]

Got pulled to this from another oil comment I made earlier today.

I worked at an automatic-transmission test facility a number of years ago, and we learned something funny about Dex 6.

We typically ran tests in 1000-hour increments, with an inspection teardown at each interval, and then re-test on fresh fluid.
When GM introduced Dex6, we used that when called for. Sometime into test segment #2, we started having leaks at the input and output seals, which had never been an issue before.

After lots of evaluation by lots of folks, the chemistry guys determined that the Dex6 had a higher level of X than previous. X is used to keep the seals soft and sealing, and it deteriorates somewhat over time. So when we did the fluid change, the trans (and existing seals) got a fresh slug of higher X, and it went to work softening the seals even further, causing leaks. IIRC Dex6 got revised to correct that.

And from my discussions with teh chemistry guys over the years - don't mix fluids. It might be OK, or it might not, but if not, you won't have the resources to diagnose it back to the fluid soup you used, so you'll likely make the same mistake again.