ATF in MT ?

[440Magnum]

Originally Posted By: MolaKule


The Aisin case is another one of those in which the engineers did not consult with the tribologist or lubrication engineer during the design or testing phase. This happens more than you might imagine and then when field failures start coming in, they scramble to dump somethiong in there until they figure out what they screwed up.


As an engineer, I can assure you engineers don't always talk to each other when they should...

But making a change that requires going back to an almost-out-of-production fluid seems even more ridiculous, because anyone designing synchros should have been aware that GL-3 was outdated and wouldn't be produced in large volumes much longer.

 

[Steve S]

It is called an E.F.U =engineering f.u.

 

[Whitewolf]

Originally Posted By: 440Magnum
My point exactly. If the MT was designed ground-up for ATF, then I see absolutely no compromise in using ATF in it. OTOH, if it was designed for GL-3 then re-specced for ATF to cure hard shifting in cold weather (its been done) then there is obviously much more chance of a compromise.

People keep throwing out claims to the effect that automatics and manuals inherently have completely different requirements, but that is ONLY true if the manual was not designed with ATF in mind. The friction characteristics of a synchro can be (and I would say often are) made to be practically identical to the friction requirements of an automatic's multi-plate clutch packs with the right choice of materials and geometry. Now when you start talking about anti-shudder additives that drastically lower the static coefficient of friction to let TC lockup clutches engage smoothly (eg. Mopar ATF+3 and ATF+4) then the will probably be different and the MT might get a case of indigestion if its designer wasn't expecting that additive in the fluid.


This is pretty much what I said earlier, the manufacturers design their product and choose their friction materials alongside the fluid that they deem to be most compatible at the time. That's why changing fluids after the fact is potentially a roll of the dice. Sometimes it works, but there is some risk attached.

 

[MolaKule]

Quote:
Now when you start talking about anti-shudder additives that drastically lower the static coefficient of friction to let TC lockup clutches engage smoothly (eg. Mopar ATF+3 and ATF+4) then the will probably be different and the MT might get a case of indigestion if its designer wasn't expecting that additive in the fluid.


But we're not talking about Transfer Case fluid.

Anti-shudder additives don't lower the static coefficient of friction, they modify the dynamic frictional characteristics.

ATF friction modifiers are complex amine derivatives, MT friction modifiers are comprised of totally different chemical compounds. WHy is that?

 

[d00df00d]

Well, is there no such thing as a synchro that doesn't work optimally (or nearly optimally) with ATF FMs?

 

[Canawler]

Molakule or Whitewolf:

Any ideas why Chrysler would spec a limited slip FM to be added to atf+4 as they do with the MT in the SRT4's (New Venture 850)??

 

[novaracer69]

i can asy that in my tranny i tried the rp syncromax and it was hard to shift. [censored] it was like driving an old chevy truck in the middle of winter. atf was spec for my 04 cavalier and works best when i use mobil 1 with 4oz.fm shifts like a dream for almost 80k so far i change it out every year seeing that i autocross it to.

 

[440Magnum]

Originally Posted By: MolaKule
Quote:
Now when you start talking about anti-shudder additives that drastically lower the static coefficient of friction to let TC lockup clutches engage smoothly (eg. Mopar ATF+3 and ATF+4) then the will probably be different and the MT might get a case of indigestion if its designer wasn't expecting that additive in the fluid.


But we're not talking about Transfer Case fluid.


Correct: TC = Torque Convertor in this context.

Originally Posted By: MolaKule

Anti-shudder additives don't lower the static coefficient of friction, they modify the dynamic frictional characteristics.


My understanding was that they do a bit modification to both static and dynamic coefficients, but I always presumed it was mostly the static side that got tweaked. To prevent shudder, the static and dynamic mu-f's need to be very close so that there's not a sudden "grab" as the clutch approaches lockup due to the static mu-f being significantly higher than the dynamic mu-f. If this is indeed done by raising the dynamic mu-f, then such fluids would, in general, be even better for MT synchro performance.

 

[mechtech2]

Has anybody ever seen a manual trans specifically made for ATF?
What I mean is with different synchro materials ?
I never heard of that.

 

[Whitewolf]

It is mostly the static coefficient that is lowered. The objective is to achieve what we call a 'positive slope'. By that we mean that when you look at the Stribeck curve you are looking to the left side of the graph and what we are looking for is a lower static coefficient compared to the dynamic coefficient, thus avoiding 'stick slip'. There are components that can have an effect on dynamic coefficient but as I don't want to (and can't) turn this into a formulation tutorial we had probably better leave it at that.
I hope that helps to some extent.

 

[MolaKule]

Quote:
Has anybody ever seen a manual trans specifically made for ATF?
What I mean is with different synchro materials ?
I never heard of that.


This what I have been trying get at and thanks for making the point directly. I too would like to see these special sychro assemblies designed specifically for ATF's.

All of the manual trannies (including racing trannies) I have seen or formulated for have synchronizer assemblies in which a male conical section (actually a truncated cone of 45 to 70 degrees angle), usually of steel or brass (or bronze), mates with a female concial section made of a copper alloy such as brass (or bronze). I have also seen synchronizer assemblies of carbon composites for small engines (1.8 L non-turbo types). (Now the exception is the heavy duty truck transmissions that use various steel materials and tempers and are lubed with MT-1/GL5 or PowerShift lubricants, but this is out of the scope for this discussion).

I have heard of developmental mt's in which ceramic synchronizer assemblies are used but never one on the road or out of the lab.

In all of these designs, the fm required has been a specialized metallo-organic compound with the proper dynamic friction coefficients such that this compound shears "PRECISELY" at the surfaces in a macroscopic fashion in order to create the proper dynamic MU(f) coefficient.

In ATF's, the complex amines provide the exact Mu(f) at the molecular or microscopic level, I.E., the fm is adsorbed as a single layer on the sliding surfaces. Wet clutch interfaces of automatic transmissions are studied using a surface forces apparatus (SFA) modified for oscillatory shear, and the results of these SFA tests is what drives the formulators.

 

[MolaKule]

Quote:
Has anybody ever seen a manual trans specifically made for ATF?
What I mean is with different synchro materials ?
I never heard of that.



The latter two paragraphs should say (edit times out on me GRRRR)

In all of these designs, the fm required for MT's has been a specialized metallo-organic compound with the proper dynamic friction coefficients such that this compound shears "PRECISELY" at the surfaces in a macroscopic (multilayer) fashion in order to create the proper dynamic MU(f) coefficient.

In ATF's, the complex amines provide the exact Mu(f) at the molecular or microscopic level, I.E., the fm is adsorbed as a single layer on the sliding surfaces (nanorheological). Wet clutch interfaces of automatic transmissions are studied using a surface forces apparatus (SFA) modified for oscillatory shear, and the results of these SFA tests is what drives the formulators to seek the best complex amine formulations.

 

[MolaKule]

Quote:
Dynamic friction is defined as the “changing of the coefficient of friction as the sliding speed between two frictional surfaces change.”

The friction coefficient of Dexron III/Mercon fluid increases as the sliding speed increases. The friction coefficient of Ford Type F fluid decreases as the sliding speed increases.

Stating the above sentence another way, Ford Type F fluid has a Low Cf at high speeds, and a high Cf at low speeds. Conversely, Dexron Type fluids have a High Cf at high speeds and a Low Cf at low speeds.

 

[TheForeman]

MolaKule, Nice to hear from Ya! I really appreciate your posts a great deal and find them informative. I was hoping you would check my previous post "Making my own Hybrid fluid for G56" but I didn't get much feedback. As you can see from my posts here I DONT like ATF for MT. Some have quoted me in this thread about adding significant EP and AW to these fluids used in MT recently speced for ATF and disagree. My view is EP and AW is always good to a certain point in a MT and current ATFs are not up to par in this respect, their additives packs are just to skimpy (just look at the VOA's of ATFs!). Sure maybe a MT will run well on ATF and shift really good too, but how will it last? even then will it not last longer with a shot Of EP and AW. My Dodge will accumulate maybe 400,000kms, by then Im sure the difference would be huge, sure a life of ATF might work but under many kilomiters and heavy loads I BET the same MT would mechanically be far more sound filled with RL MLT. Yes we probably dont need GL-5 levels of EP and AW and yes we dont want to damage synchros but we all know that both EP and AW are critical to almost every seperate fluid in a vehicle (diff, engine, etc) and greatly enhance the life of most components (everyone has been talking about lower levels of both in almost every other fluid EXCEPT MT!). So NO ATF is not the best choice mostly because VOA's and UOA's show lotsa zero's guys!

 

[TheForeman]

MolaKule, Nice to hear from Ya! I really appreciate your posts a great deal and find them informative. I was hoping you would check my previous post "Making my own Hybrid fluid for G56" but I didn't get much feedback. As you can see from my posts here I DONT like ATF for MT. Some have quoted me in this thread about adding significant EP and AW to these fluids used in MT recently speced for ATF and disagree. My view is EP and AW is always good to a certain point in a MT and current ATFs are not up to par in this respect, their additives packs are just to skimpy (just look at the VOA's of ATFs!). Sure maybe a MT will run well on ATF and shift really good too, but how will it last? even then will it not last longer with a shot Of EP and AW. My Dodge will accumulate maybe 400,000kms, by then Im sure the difference would be huge, sure a life of ATF might work but under many kilomiters and heavy loads I BET the same MT would mechanically be far more sound filled with RL MLT. Yes we probably dont need GL-5 levels of EP and AW and yes we dont want to damage synchros but we all know that both EP and AW are critical to almost every seperate fluid in a vehicle (diff, engine, etc) and greatly enhance the life of most components (everyone has been talking about lower levels of both in almost every other fluid EXCEPT MT!). So NO ATF is not the best choice mostly because VOA's and UOA's show lotsa zero's guys!

 

[440Magnum]

Quote:
Dynamic friction is defined as the “changing of the coefficient of friction as the sliding speed between two frictional surfaces change.”

The friction coefficient of Dexron III/Mercon fluid increases as the sliding speed increases. The friction coefficient of Ford Type F fluid decreases as the sliding speed increases.

Stating the above sentence another way, Ford Type F fluid has a Low Cf at high speeds, and a high Cf at low speeds. Conversely, Dexron Type fluids have a High Cf at high speeds and a Low Cf at low speeds.


What is left out of that discussion is the Cf at *zero* relative speed, aka the static Cf. The static Cf is normally much greater than the dynamic (low speed) Cf, and its that sharp difference that causes torque convertor lockup clutch shudder. The friction modifier additives in ATF+4, for example, lower the static Cf to a value much closer to the breakaway dynamic Cf, so that you don't get continuous "stick-slip-stick-slip" oscillations, or shudder. Intuitively, I would think that this type of additive would be particularly UN-desirable in a manual-trans synchro since you *want* the synchro to grab and stay stuck during the shift. But intuition != engineering, so I'd like some clarification on that.

 

[MolaKule]

The C(Fs) was purposely left out of the discussion since this was a discussion to educate laymen using the simplest terms possible, and by using example fluids at the extreme ends of the spectrum to show they had very different COF's.

Quote:
I would think that this type of additive would be particularly UN-desirable in a manual-trans synchro since you *want* the synchro to grab and stay stuck during the shift. But intuition != engineering, so I'd like some clarification on that.


As I said earlier, any of the 7.5 cSt prior generation ATF fluids work, whether highly friction modified or not, simply because the materials used in the synchros are forgiving, but these fluids are not optimal. This is similar to the situation where people claim that some 75W90 diffy fluids work in their MT's. While they may work, they are NOT the optimal fluids in the MT's.

It would be interesting to see the results of a test that compares the temps AND C(F(s,d)), of the synchros running ATF and another using metallo-organic fm's.

 

[[RT] ProjUltraZ]

i went to Tremec's page to look up my T56 and found this:

Approved lubricant - Most T56 transmission models use Dexron II ATF. Refer to vehicles owner manual or service manual for lubricant specifications.

Caution - Do not mix different brands or types of transmission lubricant. DO NOT USE GEAR OIL IN THE T56 TRANSMISSION SINCE THIS MAY DAMAGE THE BLOCKING RING MATERIAL

sorry that was a direct quote from the pdf. my oweners manual says Dexron IIE. So i hope they designed everything w/ ATF in mind, they've been making these T56s since the early 90s and a version is still used in the viper, corvette, etc

 

[aquariuscsm]

I`ve talked with an enginner at Tremec and they do spec atf for their trannies. I read (maybe on their page?) that their trannies use atf due to the needle bearings and fiber synchros instead of brass. Is the T56 the 6 speed version of the T5? Best manual trannies made imo.

 

[moklock]

Originally Posted By: novaracer69
i can asy that in my tranny i tried the rp syncromax and it was hard to shift. [censored] it was like driving an old chevy truck in the middle of winter. atf was spec for my 04 cavalier and works best when i use mobil 1 with 4oz.fm shifts like a dream for almost 80k so far i change it out every year seeing that i autocross it to.


Thanks for the info. I may just keep using M1 then as my VUE trans is almost the same as the Cav.

I assume the FM being added is the same type a limited-slip diff. uses?