Changing auto transmission oil on 72?

[clinebarger]

Originally Posted by storm9c1

Great info indeed.

But OK, I can be dense sometimes........ so bear with me.

This (link below) is what my trans shop recommended for my 4L80E. I did NOT use this. Instead I used a supply of Dexron-III that I had laying around.

http://www.wolfshead.com/specsheets/trans.pdf



So you are saying NOT to use this stuff (VI) in anything but a new 6-speed (ie: 6L80E)? I'm taken back at why he was highly recommending it (the "synthetic" VI stuff). He even told me to flush my other transmissions (mostly 4L60Es) and also replace then with this new fangled "synthetic" stuff.

Interestingly, the new fad is to indeed switch to using this "synthetic" Dexron-VI...everybody is praising it on other forums for how much longer it's "service life" is.

Basically, it's all hype then and should not be used in older transmissions? I want to get to the bottom of this debate. I'm all for not following the fads if I'm going to damage an older transmission...........

The seal hardening that ive seen is in higher mileage transmissions that have been switched to Dexron VI, A fresh rebuild would not have problems right away.....If it has the latest GM seals it WILL NOT be a problem at all if you run Dexron VI.
GM would never admit to screwing up! Not that Dexron VI is a bad fluid....Its just not 100% backward compatible.

The double "service life" claim is B.S......Most ATF's that claim the be full synthetics use ONLY group III base oils.....Mobil 1 ATF is a good example.
If you consider group III base oils "synthetic" Dexron VI is at best a synthetic blend?????