I used Valvoline Syngard with success for 230k hard miles in one allison.
Are old-school auto transmissions with non-lockup torque converters harder on AT fluid?
- Thread starter SumGuy
- Start date
Many performance builders recommend dex3 in 47 and 48re's, the overdrive/lockup version of a 727. Pretty sure my 95 Dodge dipstick says dex3 on it.
Again, when you have a lockup converter, what is the technical focus on the ATF? What properties are you looking at? And is that focus or those technical properties also at the top of the list for what a non-lockup transmission is looking for?
How the Converter Clutch applies matters, PWM apply & continuous slip strategies shear the ATF, Older on/off style systems don't shear the ATF more than any other clutch in the transmission.
727 based O/D lock-up units use a on/off TCC control & technically don't require ATF+4. Dexron III provides better/more positive shift quality.
727 based O/D lock-up units use a on/off TCC control & technically don't require ATF+4. Dexron III provides better/more positive shift quality.
I think at low torque and higher rpms ~2800+, they basically are "locked" and pretty efficient as these cars had pretty low stall speed rpms. My 1981 Omega V6 had a 3spd non locking auto and it got high 20's hwy mpg which was pretty good for a box with a carb'd v6 spinning just under 3k rpms. Above 60mph the rpms in top gear didn't "flare" much at all with even nearly full throttle. My 3spd 1995 Neon had basically the same gearing and did lock the TC and got low 30's mpg with with the FI 2.0 4 cyl in a bit more aero shape.
I think if you could run the engine in the 2-3 times stall speed rpms, an open TC would be pretty efficient even transmitting full power? But I guess there's plenty of inefficiency in the engine when its up around 4-5-6k rpm.
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JHZR2
Staff member
My 96 says ATF+3 and Dex II.
I went with ATF+4 and have been happy.
This is what the OM/Dipstick says:
Mopar ATF Plus type 7176 or Dexron II.
Frankly I’m surprised that they mentioned Dex II in 1996, as I’m pretty sure Dex IIIH came out around then.
So what would you run? I’ll probably use the same in my old MB cars as they all specify Dex II.
Mopar ATF Plus type 7176 or Dexron II.
Frankly I’m surprised that they mentioned Dex II in 1996, as I’m pretty sure Dex IIIH came out around then.
So what would you run? I’ll probably use the same in my old MB cars as they all specify Dex II.
Again you are turning the focus back to lock-up converters. I want to know how Dexron 3 and 4 and ATF+4 fare in non-lockup converters from a longevity / shear standpoint.
How much "damage" does a torque converter (a non-lockup torque converter) do to ATF?
JHZR2
Staff member
ATF+4 is a tightly controlled and robust spec. I’d have a hard time figuring out a rationale why a better spec fluid would fare worse. Both Dexron IIIH and ATF+4 were designed to be more shear-stable and longer-lasting.
Is any AFT today formulated with an eye towards the operational requirements of non-lockup torque converters?
OR - are lockup and non-lockup torque converters indistinquishable in their ATF needs?
I have seen posts regarding the differences between the dexrons and ATF+4 in shear tests and they appear to be significant.
OR - are lockup and non-lockup torque converters indistinquishable in their ATF needs?
I have seen posts regarding the differences between the dexrons and ATF+4 in shear tests and they appear to be significant.
ATF+4 & Dexron VI would surely win a shear down contest with a conventional Dexron IIIH.
You brought up A727 derived overdrives?? These units run so dirty that extended drains are detrimental.
No, I didn't bring up the overdrive situation, I'm not interested in that. I don't know when (what year) the 727 overdrive came out, but it wasn't in any Chrysler passenger car from the 1960's that I'm aware of. I believe they were electrically engaged, and maybe they even had lockup-type torque converters?
Canada tire sells 5-quart jugs of Mobil brand ATF+4 ($75) and Dexron 4 ($60). A 727 needs 1.5 or maybe 2 of those jugs. Is the ATF+4 worth the extra $15 for a 727?
JHZR2
Staff member
If you care about it, and it’s back-specified properly, then yes.
JHZR2
Staff member
To me it’s dubious that any new spec would be looking to provide, first and foremost at least, increased protection for obsolete equipment.
What they do tend to do, however, is make the new specs more robust, better performing, etc. Relative to engines and transmissions, generally that trend is more power dense, higher temperature, lower viscosity, less buffer of viscous cushion between parts, higher rpm, higher shear, more oxidizing, etc.
But it would seem that modern fluids all are focused on superior shear stability. And that is a super-important metric for non-lockup TCs obviously….
I'm not necessarily looking for "protection". I'm looking for operational suitability.
The armchair response is always that the new specs are always backwards compatible and hence of course the current-spec oil will be fine in a previous-generation transmission, without considering the fundamental difference (lockup vs non-lockup) torque converter and what does that actually mean for the oil.
It would seem that the current "fill for life" ATF (no fill port, completely sealed transmissions) would need a very shear-stable forumulation, perhaps that task is easier (very much easier?) when you're dealing with a lockup converter, and could not be done otherwise?
JHZR2
Staff member
IMO you’re way overthinking.
Old ATs sheared fluid like crazy. New ones may do it less, but they still shear the fluid if not locked up. They use basestocks that are more shear resistant, more oxidation resistant. What else needs to be said?
You’re speculating that there’s something better or something that could be more optimized, without a semblance of realism regarding what metrics or attributes that could be that are not the improvements that modern fluids have offered.
Sorry, it’s just not really sensible.
I'm asking what is a better (best?) oil for a 1960's Mopar 727 transmission. Dexron 3, Dexron 4, or ATF+4. Or something else.
JHZR2
Staff member
No, from what I’ve read, at least in my interpretation, you have been asking if some ATF is optimized for an obsolete design transmission, and if newer spec lubes are compromised for these older transmissions.
You’ve been told over and over that shear and oxidation are the biggest challenges, and that new ATFs handle both better.
But it seems like you don’t like that answer (?).
But I’ll say again, if any fluid will give the best in terms of robustness to shear and oxidation, and a semblance of hope for back-spec to the friction characteristics of an older Mopar AT, it will be the ATF+4, imo.
There are some modern instances of Dexron II/III type fluids (e.g., redline offerings), but the best bet OTS is the +4.
Dexron III-Dex/Merc & change it often.
Torqueflite's (727's and 904's) called for Dexron. ATF+4 didn't come out until the Torqueflite was out of production and has different friction characteristics than the Torqueflite was designed for. I would use Dexron VI before I used ATF+4 in one. If it was me, I would use a Dex/Merc fluid and change it regularly like @clinebarger said.
If you want to use a better fluid than standard Dex/Merc, you could spring for Mobil Delvac 1 ATF which is a full synthetic Dexron type fluid.
https://www.amazon.com/Mobil-112810-Synthetic-Automatic-Transmission/dp/B009IE2MX2?th=1
If you want to use a better fluid than standard Dex/Merc, you could spring for Mobil Delvac 1 ATF which is a full synthetic Dexron type fluid.
https://www.amazon.com/Mobil-112810-Synthetic-Automatic-Transmission/dp/B009IE2MX2?th=1
Would TES-668 be an optimal, shear resistant, higher viscosity atf for the 727 transmission?
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