ATF 4 versus Dextron III whats the difference?

This thread is old, but in trolling for info on ATF+(whatever) VS Dexron (whatever) in Dodge trany's; I ran across it and can't believe the mis-information it contains.

First up, a simple call to 'an un-named manufacturer' (the person spoke from anonymity because of Licensing (see 2 below)) resulted in MS-9602 - M5040901 - GMN-10060 the specifications for ATF by 'the big three' and a comment that there is not really a dang bit of difference in any of them, except for the new Dexron VI (see below).

Second, Dexron(R) / Mercon(R) & Type F(R) / ATF+ or ATF Plus(R) are all COPYRIGHTED specifications that oil companies MUST pay for the right to put "Compatible" or "approved" on the label of their products. Of course those copyrights are owned by, go ahead and guess - thats right; Chevrolet, Ford, and Chrysler (respectively). This was admitted by that un-named company not listed above.

Third, ATF+4, Dexron VI, and Mercon V are all FULLY SYNTHETIC oils; they have to be because of reason 4 below.

Fourth, OIL is OIL - it don't matter the name you put on it, as long as it meets certain specifications (ASTM "kinematic viscosity of oils" Specifications in this case). Those specifications are (in no particular order) Gravity (or weight), Viscosity at a given temperature, and heat dissipation.
Now in looking at the previously mentioned ATF's, the ONLY difference is the viscosities at given temperatures, are:
Code:

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Type | Viscosity |  @ 40C  | @ 100C
ATF+4:  V204, cST@40C 33.24 cST@100C 7.51
MercV:  V205, cST@40C 33.20 cST@100C 7.50
DexIII: V201, cST@40C 34.70 cST@100C 7.70
Type F: V150, cST@40C 36.00 cST@100C 7.20
DexVI:  V145, cST@40C 29.50 cST@100C 5.83 *1

Amsoil: V168, cST@40C 38.90 cST@100C 7.60
RoyalPurple: V210, cST@40C 32.50 cST@100C 7.50
Redline syn: V197, cST@40C 32.50 cST@100C 7.20
Redline C+ : V213, cST@40C 32.30 cST@100C 7.50
Redline Race: V177, cST@40C 53.70 cST@100C 10.00

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So what does all that mean? It means that the differences between any of these ATF Fluids is negligible with the exception of Dexron VI (IE: they all work in any trany) the only thing you will notice is a small change in the shift points and or hardness in the shift; because of how thick the fluid is at any given temp. Notice that "Race" fluid is "thicker" at higher temps, and will give you a harder shift.

Note 1: GM Intentionally made Dex VI non-compatible with other fluids - IE: Don't use it in anything else because it is way too thin.

Note 2: We used to use Type "F" in the Powerglide & TH350/400 & 727TF to improve the shift (before all the fancy race fluid's came out).

In closing, and with all due respect to everyone's opinion on the matter: The laws of Physics (Hydrodynamics) are not influenced by opinions. Because transmissions operate from a well known set of laws, and within a wide range of tolerances - the difference between one fluid and another in any given transmission would still be well within spec's.

Very interesting information, Charon9
Thank you for posting it.

I am not sure I agree completely with it,
primarily because the different ATF's have been found to have different effects on
'torque converter shutter'
and I have experienced this personally with
ATF+2 versus Mobil One Synthetic ATF in a 46RH.

I am also not confident that you can categorize ATF performance inside the torque converter strictly on viscosity at different temperatures,
and I am not confident that viscosity alone is all you need to know for gear and bearing lubrication.
Other measures like film strength:

http://en.wikipedia.org/wiki/Timken_OK_Load

have been proven important in other high load applications, and I have seen this personally in mining equipment.

It has been awhile, but I did once read the 14 page SAE paper # 982674 that Chrysler, Lubrizol, and Texaco Lubricant engineers wrote about 9602 ATF (called +4) was superior:

http://u225.torque.net/cars/tech/trans/982674.pdf

Most of what I know about lubricants I learned from Lubrication Engineering, Inc of Texas, so I might be biased.

I had a long interesting telephone conversation years ago with an engineer at
Universal Lubricants,
the maker of Lubegard 'Red Bottle',
the company founded by an ex-Mobil One engineer who got a US gov grant to turn agricultural plant oils into a substitute for (no kidding) Sperm Whale oil that used to be in ATF formulations.

Your post indicates you are interested in ATF for Dodge automatics (and open minded)
so I would urge you to read 982674 too,
and give your comments.

I am not completely sold on 9602 myself now,
because within 1200 miles after I put new 9602 ATF+4 in my (very high mileage) 46RH in place of ATF+3 plus Lubegard,
the friction facing materials came off my torque converter lockup clutch.

RL Keeping me busy here, so slow to reply.

I try to stay open minded that is for sure, I have seen a lot in this business and bet I will see lots more before I die.

"Other ATF Specs" - your right, I did not post those spec's or the testing procedures for ATF on it - it is much more complicated than the simple Timken bearing test; great test for bearings alone, but don't fly on most automotive stuff as there is more involved.
I do know that oils are made by these test specs, and 2nd grade oils are normally sold by the 'other guys' (store brands mentioned) not the big guy's.

I think we will disagree with each other on viscosity; the report you posted even agrees with me on that as it quotes over and over how viscosity performance (over a temperature range)was the main thing they were looking for. (Pages: 3 / 5 "Testing methods: Viscosity Retention - etc) - other things mentioned within.

Performance between different brands is a given variable - I have seen "Valvoline" work fine, where "xxxxx" wouldn't work at all. It all comes down to quality control, and standards of the company. There are companies with high standards of control and those that say "Look its red, must be ATF."

A bit in detail:
Viscosity is the main issue when dealing with an automatic transmission. Fluid dynamics inside the torque converter change based on the viscosity of the fluid over a range of temperatures. If the fluid is too thick, it drags on the stator and if it is thick enough the car won't even start (have seen that) // by the same token if the fluid is too thin less kinetic energy (hydraulic energy) is transfered to(from) the stator so the "stall" goes up (sometimes WAY up) - we have used jack or power steering fluid to raise the stall in some roundies.
The physics behind this is noted as: r N5 D2 -- where R is the viscosity (called weight) of the fluid,
http://en.wikipedia.org/wiki/Torque_converter

To put this simplistic: If you take 100 square feet of 'air' and compress it down to about 1.5 cubic feet you end up with about 1500 PSI of pressure. If you took 100 sq feet of ATF and compressed it down to 1.5 cubic feet; well you would need metal designs from Star Trek to hold the pressure - because fluids do not really compress. Where if you took a 'thinner' ATF it would not be as much pressure - try it with water, then ATF just for giggles.

Or try this simple test.
Take any standard transmission (normally 90w oil) and put in 140w "hypoid" rear end oil. Drive it in summer, then try to shift it cold in winter (I have seen people break the shifter trying)

This brings us to "Sheer" / what the Chrysler report you quoted said, what I tried to avoid to some degree / and what the Timken test starts to look at. Please note that ATF Tests are far more excessive than the Timken test.
Sheer is where the fluid breaks apart (at a molecular level) because of the pressure it endures and or temperature (to be fair). This is where the additives, mentioned in that report, come in. When the fluid breaks down, it looses viscosity performance because it is now two separate fluids again (although mixed).
Again, viscosity - this time over a specific period of time.

Lubrication is the next point I think you made, and a good one as it shows how ATF has three functions (rust prohibiting being the third - not discussed). Not only must ATF retain its viscosity, it must provide for lubrication as well (modern chemical engineering). Again however we are dealing with quality control between the brands.

The last point I will make before telling two short stories is that these issues are very well understood, and an attempt at making a 100,000 mile fluid is what ATF+4 is all about (and it is NOT suggested you try to run it that long - be smart). I will admit that I know nothing about mining equipment, or heavy equipment either. I worked in different auto shops over the last 35+ years and built a "lot" of 1/4 1/8th and roundies.

Story 1: I don't remember the car, but it called for something other than DexIII - but that is what we put in it. Now, this was valvoline as we got a deal and had a pallet of it in the back. Come a few months later the same basic car came in again, and we used non-valvoline DexIII in it. It would not shift, would slam into gear, if it did shift, and the lockup never did. We had to flush it and put valvoline DexIII back in it - no problems.
So different problems can be explained by the 'brand' as much as the type.

Story 2:
My reason for coming here in the first place was that I have a used 99 46RE (Ram truck). It had a shift problem so I changed the fluid and filter, went back with ATF+4 (some lower brand name; was on sale /shrug). In any case the thing would shift 'light' when cold - and not at all when hot (less than 2 miles driving). It would also flutter or seek on shift during the mid temp's. I also read that there is a problematic check ball near the radiator so decided to put on an external cooler & flush the system while I was at it.
So I replaced all the fluid with DexIII Maxlife, and test drove it. Now the shifts were very firm, and no 'shutter' on TC lockup (was firm there too) - downshifts pulled power no problem. The problem returned on longer trips (15+ miles) - cooler and thicker fluid simply extended the drive time.
At this point I called a trans friend of mine and he said it was the gov sol - so I pulled it (screens were full of trash (from the flush?)) in any case I cleaned it and put it back together with 1/2 DexIII and 1/2 B&M Trick Shift. Now you can't even feel it shift, unless you hit the gas then it shifts like the DexIII (Firm).
Hindsight being what it is I should have just dumped the lower quality fluid, replaced it with a high quality brand (still with a touch of B&M) and I bet I would have been fine.
Moral to this story: Brand name does matter.

For me all the fluids are the same (exception of Dexron VI) the thickness changes the shift and that is about it - same reason you used to change the spring tension on the valve body to change the shift point (shift kits). Price / Brand, mean higher quality control - more to specs.
IMHO the report you linked confirms that, but that may not mean we will agree

It has been a year since I posted my thing on ATF+ vs DEX III; figured I would drop by and post an update on things.

One thing I have learned that I did not know when I posted this, is that mixing the fluids can have one unexpected result; it seems that the additives (stabilizers, anti-foam, cleaners, etc) and cause corrosive byproducts when placed under heat and pressure. (I would suspect this was intentional - if I was one of those types to think such things).
In any case this can cause seals to leak (internally and externally).

I'm happy to say however that after a year of running 1/2 (Valvoline) DEX III + B&M Synthetic trick shift, everything still works great.
I really suspect those having problems with adding other than ATF+4 are using store labeled junk (even if it is labeled as ATF+4). If you decide to play with one of these electronic tranny's (fluid wise) I would suggest you understand what we posted and what it means; or leave it alone.

@ Charon9 -
I too have a 99 Dodge (Durango) with the same trans (46RE) I think. I've had it since last August & acquired it with a trans leak. My wife & I also have an '07 Caravan that takes the +4 fluid. I've been just using that to top off my Durango also. We've just recently started hearing a ticking noise in the transmission, which I have deducted as the trans pump (checked the flex plate). I could be completely wrong though - transmissions are not my forte. Just yesterday my wife was highway driving (not far from home) & the trans started skipping/slipping between 2nd/3rd gears. by the time I got home from work - the trans was completely cooled down & gave me no issues at all, except for the ticking noise after parking it. So I had the theory that the incorrect (or store brand) fluid could be causing the issue. Any thoughts?

been reading the posts. My previous truck 92 Dodge diesel wore a hole in a trans line(1/2 inch line)after i fixed i put in dexron , used this for 30 years. Trans would act weird and after i bought my 24 foot enclosed trailer it slipped so i thought the trans was bad. Pulled it out and found nothing wrong, put new seals and back in, still acted weird.While looking at the specks in the manual it said in big letters do not use Dexron but use Chrysler's,Just a part number then no ATF-3 or 4. So bought three gallons, drained and put the new fluid in, WOW what a difference. Trans shifted crisp and no slip and sold at 189,000 miles. My current truck an 06 3500, trans went out with burnt front clutches at 38,000 miles, different issues( cranked the pressure up) but i still use the recommended ATF-4 fluid.I'm no expert but if it works i use it. I still use type F in the race trans.

I have had several Chrysler products over the years and anytime I used anything OTHER than ATF+4 in a car that calls for it I have had problems. MY Caravan had a shudder on TQ conferter lockup, It went away with the MOPAR ATF+4.
Personally I would not use anything else. That being said I have had the fluid changed in my 02 Ram ever 30-40k, I have no idea what brans the shop used but it was ATF+4. !60k miles and stil lgoing strong.
Scott

ATF+4 is a good oil i have 218K on my dakota. never changed or added to. i do drive about 70% highway.

ATF+4 is a highly friction modified (HFM) fluid. It has more friction modifiers in the add pack than, say, Dexron fluids. IOW, the friction materials in the trans see it as "more slippery", as far as clutch engagement, etc. Always use the recommended ATF in modern transmissions.

Anybody notice how old the original thread is? Subject has been beat to death.

The fact that Chrysler says ATF+4 is backwards compatible doesn't mean it's the best fluid for older transmissions, it just eliminates the need for your dealer's parts department to stock lots of different fluids.