Dando continuidade aos estudos relativos ao t�pico seguem algumas informa��es obtidas no site:

Chrysler transmission fluids: 7176, ATF+3, ATF+4
Chrysler automatic transmission fluids: 7176, ATF+3, ATF+4

ATF+4

GM Frazier wrote:

Group I base oils can have a mix of different hydrocarbon chains, with relatively little uniformity; these oils are the least refined. They are usually not used for autos.

Group II are the most common base oils in �dino juice,� with good performance in most areas except cold temperature viscosity.

Group III are called synthetic, and have high molecular uniformity and stability. Group III oil bases are used in most synthetic oils.

Group IV are chemically engineered stocks, arguably with the highest performance and longevity.
For the full story behind the development of ATF+4, please see SAE paper #982674. It is simply packed with interesting data about the development of ATF+4. Here are a few tidbits:
The initial development was done using Shell's XHVI base oil. Only much later were other Group III base oils approved. (Currently, SK in Korea and PetroCanada are the only additional approved base oil suppliers.) The use of Group III base oils is probably the leading cause for ATF+4 being a more expensive fluid than ATF+3 (which according to the paper uses a Group II base oil).
Lubrizol developed a new shear-stable viscosity index (VI) improver
specifically for ATF+4. The initial tests of this VI improver in the
MS9602 test fluids were so remarkable that Chrysler modified the then-current ATF+2 spec (MS7176D) to include it. Thus ATF+3 (MS7176E) fluid
was born; it remained the factory fill until the introduction of ATF+4.
In testing done during development of ATF+4, Chrysler noted the following viscosity loss from shearing for the following ATFs (20 hour KRL Shear Test):

Dexron III - 40% loss
Mercon V - 19% loss
Type 7176D - 32% loss
Type 7176E - 14% loss
Type 9602 - 10% loss

You can see what a significant impact the new viscosity improver had on ATF+3 when you compare the 7176D and 7176E numbers. From the standpoint of viscosity loss alone you can see why Dexron III should not be used in transmissions that require ATF+3 or ATF+4. In terms of other basic performance parameters, ATF+3 (7176E) comes the closest to ATF+4, with Ford�s Mercon V a close second. [Which doesn�t mean that Mercon is acceptable.]
The goal in developing ATF+4 was to create a fluid that would match the performance characteristics of the current fluid (Type 7176D), but would retain those characteristics for at least 100,000 miles. The paper specifically notes that the anti-shudder properties of ATF+3 are usually degraded enough by 30,000 miles to cause noticeable shudder.
Contrary to popular myth, one of the stated goals of Type 9602/ATF+4 fluids was that it would have the same frictional characteristics as ATF+3. The paper explicitly states that this was because new clutch materials would not be introduced for this fluid and it had to be backwards compatible with ATF+3. Graphs in the paper show that the friction coefficient of fresh ATF+3 and ATF+4 is essentially identical, but as the fluid ages ATF+4 retains the �as new� coefficient while ATF+3 degrades.

The paper noted that one alternative was to use synthetic Group IV base stock, which are even more expensive than the ATF+4 solution, which provided Group IV style performance from Group III stock. ATF+4 meets strict low-temperature, oxidation, and volatility performance requirements and relatively low cost � believe it or not.
Valvoline now makes an ATF+4 fluid.
ATF+3

ATF+3 is a friction-modified, high-quality transmission fluid similar to the current fluid in most respects; but it wears out more quickly and has less desirable cold viscosity (to simplify: is too thick when cold). ATF+3 can be approximated by Dexron plus an additive but this does not save much money and is not as desirable as using the correct fluid to begin with.
Dexron itself is the General Motors-specified fluid from far back in automotive history. While it was once the standard for all American autos, that time has long passed, with Ford settling on Mercon and Chrysler on ATF+3 (and now ATF+4); other manufacturers also require their own fluids.
Engine oil has been used as an automatic transmission fluid, again in the antiquity of automatic transmissions; it is still used in manual transmissions, but generally a single-grade oil is used.
Usage

You can use ATF+3 with all older Chrysler transmissions (except as noted below - some Jeeps). ATF+4 is another story. This is from a Chrysler engineer:

If there is a doubt about which grade of ATF to use, follow the owners manual recommendation. AFT+4 in certain specific tests was shown to be incompatible with certain seal material. This incompatibility may cause a premature failure depending on the duty cycle of the vehicle. The fluid will work as intended however, it may cause a seal failure.

Chrysler is not the only company to require a unique transmission fluid. Dexron has long since passed its prime, and modern transmissions require modern fluids, which more refined properties. Toyota, Ford, Nissan, and other major automakers also require unique fluids.
Additives

David Castater noted: �I used Lucas transmission additive on the recommendation of my local Kragen counterperson... What a mistake!!!! We started seeing shudder at 55+ mph. The dealership told us it was the torque converter dropping out of lockup and the tranny would fail and should be replaced ($3,000). This was a dealer purchased rebuilt transmission less than 4 years old! My local AAMCO manager changed the oil and filter, added a"friction modifier", and reprogrammed the computer. No problems since!!�
John C. Lai wrote that LubeGuard, used with Dexron by AAMCO, is not a good substitute for ATF+3, either: "...although Lubeguard claims on their website that their product will convert Dexron to become an ATF +3 (7176E) equivalent, they actually have no test data to back that up. In fact, their head engineer told me that the tests they did were conducted in the early 1990s with the first version of 7176, several years before ATF+3 was developed. So, they have no basis for their claims of ATF +3 equivalency.

Dessa p�gina, em resumo, entendo que o Dexron III n�o substitui o ATF+3, a n�o ser que seja adicionado um aditivo modificador de atrito.
Reparem ainda na lista de percentual de perda de viscosidade logo no inicio do texto, o ATF+4 perde 10% e o Dexron III perde 40%.

Mais um motivo pra pagar R$40 no litro do ATF+4.

Mas n�o paro por ai, aguardem............

Abra�os e bom feriado!!!