Are old-school auto transmissions with non-lockup torque converters harder on AT fluid?

[SumGuy]

So discussing ATF for 60's transmissions has no value because they're ancient technology, but BITOG is loaded with discussions for the oil used in the presumably also ancient engines in front of those transmissions.

Regarding terminology, is it ok to say "dexron 4" instead of "dexron VI" ? I just don't see the point of using roman numerals. I also don't get the difference between "Dex/Merc" and dexron (from a naming pov). Why the mashup?

This old post has a lot of information (or opinion, maybe credible/accurate, maybe not):

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/629438/1.html

Planetary gears that run most of the time in over-drive (old 727's didn't have overdrive) and lockup torque converters (which again old 727's didn't have) are other things to consider. Some ATF's have detergent, wax, some don't.

 

[ripcord]

So discussing ATF for 60's transmissions has no value because they're ancient technology, but BITOG is loaded with discussions for the oil used in the presumably also ancient engines in front of those transmissions.

Regarding terminology, is it ok to say "dexron 4" instead of "dexron VI" ? I just don't see the point of using roman numerals. I also don't get the difference between "Dex/Merc" and dexron (from a naming pov). Why the mashup?

This old post has a lot of information (or opinion, maybe credible/accurate, maybe not):

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/629438/1.html

Planetary gears that run most of the time in over-drive (old 727's didn't have overdrive) and lockup torque converters (which again old 727's didn't have) are other things to consider. Some ATF's have detergent, wax, some don't.

If you want to write the Roman numerals out, it would be Dexron 6.

 

[MolaKule]

So discussing ATF for 60's transmissions has no value because they're ancient technology, but BITOG is loaded with discussions for the oil used in the presumably also ancient engines in front of those transmissions.

I think discussions about old technology are worth while, but I don't see anyone poopooing the idea.

Regarding terminology, is it ok to say "dexron 4" instead of "dexron VI" ? I just don't see the point of using roman numerals. I also don't get the difference between "Dex/Merc" and dexron (from a naming pov). Why the mashup?

The official designation is "Dexron VI," when referring to the improved and more stable Dexron version established by GM, and having a viscosity of about 6.1 cSt@100C.

Dex/Merc refers to the previous Dexron III-X series having a viscosity of about 7.3 cSt@100C, and was interchangeable between most GM and Ford transmissions at the time.

"GM Automatic Transmission Fluids (ATF)​

The original DEXRON (B) transmission fluid was introduced on April 1, 1967. Over the years, the original DEXRON (B) was supplanted by DEXRON-II (C), DEXRON-II (D), DEXRON-II (E), DEXRON-III (F), DEXRON-III (G), DEXRON-III (H), DEXRON-VI (J), DEXRON HP, DEXRON LV ATF HP, and DEXRON ULV, which is the latest fluid to date. GM has upgraded the DEXRON's specifications over time. The newer fluids are not always backward-compatible with previous fluids. Newer 6, 8, 9, and 10-speed transmissions, as well as plug-in hybrid (PHEV) and electric vehicle (EV) transmission technologies, require specialized fluids to operate properly. There remains a market for older fluids that claim to meet the earlier fluid specifications. See the details below for the backward compatibility of each fluid..."

found at https://en.wikipedia.org/wiki/DEXRON with plenty of good reading history and references.

I would concentrate on ATF performance and less on minutae.

This old post has a lot of information (or opinion, maybe credible/accurate, maybe not):

...Planetary gears that run most of the time in over-drive (old 727's didn't have overdrive) and lockup torque converters (which again old 727's didn't have) are other things to consider. Some ATF's have detergent, wax, some don't.

All ATF's have detergents and dispersants. I don't know of any ATF's that have wax, so you are misinformed.

 

[ripcord]

Would TES-668 be an optimal, shear resistant, higher viscosity atf for the 727 transmission?

It would be a good, if expensive choice. Castrol Transynd 668 has a cSt value @100c of 6.9 which puts it in the high viscosity category. Castrol says it's backwards compatible with TES-295 so is appropriate to use in Dexron II or III applications.

 

[56Cummins]

I like the thicker fluids. A synthetic dex3(mobil1,amsoil...) will probably have more shift feel that atf4.

tes295/668 would be great choices also.

All of those are amongst THE BEST for a 727.

 

[MolaKule]

I like the thicker fluids. A synthetic dex3(mobil1,amsoil...) will probably have more shift feel that atf4.

tes295/668 would be great choices also.

All of those are amongst THE BEST for a 727.

Shift feel is determined by the timing and programming of the shift solenoids (or valve timing), internal fluid pressures, and the Dynamic Friction Coefficient that is designed into the fluid. Viscosity has little to do with shift feel.

 

[SumGuy]

So there was no dexron 4 or 5? It went from 3 to 6?

 

[ripcord]

So there was no dexron 4 or 5? It went from 3 to 6?

Yes, it skipped from III to VI

 

[SumGuy]

Does a torque converter want a high-viscosity, or a low-viscosity oil? What is the effect of oil viscosity on torque converter efficiency (assuming we're not talking about lock-up converter) ?

Would an ideal automatic transmission separate the torque converter from the rest of the mechanicals - giving the converter it's own fluid (and pump and cooler if need be) allowing for different-spec oils for the converter vs everything else?

I understand that some (or most?) FWD cars don't give the differential it's own sump and oil supply, instead it's shared oil with the transmission. I'm thinking that would create extra complications in formulating an ATF spec for that sort of arrangement (gear oil being somewhat more viscous than ATF I would think).

 

[clinebarger]

Synthetic fluid is a waste of money on a unit with so many loaded Thrust Washers.

 

[NissanGuy91]

Synthetic fluid is a waste of money on a unit with so many loaded Thrust Washers.

Why would loaded thrust washers make synthetic atf a waste?

 

[4WD]

In the Dex III era - guys here that towed heavy switched to
Mobil 1 ATF. It seems to be on the way out with a declining market - so if I had such a need - I would stock up.
Here is a sale:

https://www.autozone.com/motor-oil-...2_0_0?searchText=Mobil+1+ATF&redirectUrl=true

 

[CheezWhiz]

does torque management protect the atf?

 

[nthach]

We had two Mercedes with the 722.3/4 transmissions without lockup(and no overdrive even). They did fine on Pennzoil or Castrol Dex III/Merc fluid. If we still had them, I’d run MaxLife or even TranSynd in those.

 

[ripcord]

In the Dex III era - guys here that towed heavy switched to
Mobil 1 ATF. It seems to be on the way out with a declining market - so if I had such a need - I would stock up.
Here is a sale:

https://www.autozone.com/motor-oil-...2_0_0?searchText=Mobil+1+ATF&redirectUrl=true

Mobil 1 Delvac ATF is the current equivalent/improvement on the old Mobil 1 ATF product. It's TES 295 and 468 approved, so a big improvement on the original DEX IIIh.

 

[Number_35]

They are both bad for ATF. Extreme heat oxidizes the fluid and shear thins it.

In the case of the non-lockup torque converters of old, fluid slippage meant the fluid consumed more energy and thus resulted in a larger temperature rise.

However, modern additive chemistry and better base oils, starting with Dexron VI, has improved both to the point where we see much less shear thinning and oxidation, and we cannot forget the more stabilized friction modification chemistry as well.

There was an article perhaps 30 years ago saying that old-school ATF was made of whale oil, and later replaced with oil made from lard subsequent to restrictions on hunting whales.

The same article claimed that the transmissions run on whale oil lasted until about 100,000 miles, whereas those run on lard-based ATF failed around 70,000 miles.

This may have been print advertising for an ATF additive - I don't remember where I saw it.

Even if true at the time, it's probably moot now due to synthetic ATFs.

 

[nascarnation]

There was an article perhaps 30 years ago saying that old-school ATF was made of whale oil, and later replaced with oil made from lard subsequent to restrictions on hunting whales.

The same article claimed that the transmissions run on whale oil lasted until about 100,000 miles, whereas those run on lard-based ATF failed around 70,000 miles.

This may have been print advertising for an ATF additive - I don't remember where I saw it.

Even if true at the time, it's probably moot now due to synthetic ATFs.

It was a real scramble to reformulate ATFs after the whale protection kicked in.
On the other hand I was on vacation in Alaska last year on a whale watching boat and the 40 yr old native guy on there told me it's amazing how many whales are around now compared to when he was a youngster.

 

[4WD]

There was an article perhaps 30 years ago saying that old-school ATF was made of whale oil, and later replaced with oil made from lard subsequent to restrictions on hunting whales.

The same article claimed that the transmissions run on whale oil lasted until about 100,000 miles, whereas those run on lard-based ATF failed around 70,000 miles.

This may have been print advertising for an ATF additive - I don't remember where I saw it.

Even if true at the time, it's probably moot now due to synthetic ATFs.

Think that’s some of the roots for LubeGard esters

 

[supton]

does torque management protect the atf?

I don't see how. That limits how much torque the engine can make while in lower gears and/or at lower vehicle speeds. Which could lead to less heating of the ATF during unlocked conditions, sure. I don't know if my Tundra had TM but I know it would not use lockup in gears 1-3 and it absolutely loved to unlock the convertor as opposed to downshifting--it'd rather roast the fluid than use mechanical advantage. [I'd say it was stupid but Aisin transmissions are relatively robust and seem to shrug off heat, so there's that.]

I understand that some (or most?) FWD cars don't give the differential it's own sump and oil supply, instead it's shared oil with the transmission.

I believe that is true for most of the FWD's. A few had separate sumps (I owned one) but usually it's the same fluid as the transmission. Hypoid gears apparently have unique requirements, but regular gears, and bevel gears, are much more forgiving. If nothing else, warmer fluid is thinner, making for less drag, which makes for better mpg (not sure how much that really matters for an automatic but in a stickshift it might).

 

[PandaBear]

I don't see how. That limits how much torque the engine can make while in lower gears and/or at lower vehicle speeds. Which could lead to less heating of the ATF during unlocked conditions, sure. I don't know if my Tundra had TM but I know it would not use lockup in gears 1-3 and it absolutely loved to unlock the convertor as opposed to downshifting--it'd rather roast the fluid than use mechanical advantage. [I'd say it was stupid but Aisin transmissions are relatively robust and seem to shrug off heat, so there's that.]

I believe that is true for most of the FWD's. A few had separate sumps (I owned one) but usually it's the same fluid as the transmission. Hypoid gears apparently have unique requirements, but regular gears, and bevel gears, are much more forgiving. If nothing else, warmer fluid is thinner, making for less drag, which makes for better mpg (not sure how much that really matters for an automatic but in a stickshift it might).

My understanding and experience is that ECU reducing power output while shifting really helps most Toyota / Aisin vehicles out in transmission durability. My dad's Taurus (with bad transmission reputation) doesn't and based on how the shift feels, it is smooth and almost like it applied clutches with overlap ratios to smooth things out at the expense of wearing out clutch material. So electronics do help durability in this aspect.

The only vehicle I had with 2 sumps for AT and differentials but that's probably because that vehicle had a non US model with 4WD (Corolla). That differential sump supposedly also last 60k only but most people ignore it. I have paid someone to change it once at like 160k and it didn't cause anything good or bad to happen. The Corolla would likely have lasted the same 270k+ miles before I ended up crushing it due to rebates and getting a larger vehicle for family need.

Today's ATF is much better, transmission is much better, that unless you are running CVT, a reputable company made step transmission on a sedan would last a long time.