With shared or independent Differential Lubrication.
Very Basically Talking, there are Two types of Lubrication Systems for the Differentials, that comes integrated onto the Automatic Transmission's Case, or "Transaxle" as those combos are known nowadays.
► First Type: The Differential has its Own Lubrication, independent from the Rest of the Transmission's Lubrication System and also uses its own independent Lubricant.
► Second Type: The Differential shares the same Lubrication system and the same Lubricant that is used for the Transmission.
Also, very Basically Talking, there are Two types of ATF Additives, which independently from the benefits they could do and their disadvantages; the ATF Additives could be divided in Two Big Groups:
► First Group: Are all of those ATF additives which actually "Thins" the ATF (getting Lower Viscosity) and works as detergent. In this group, you can find additives such like "Trans-X", and many more.
► Second Group: Are all of those ATF additives which actually mades the ATF to be "Thicker" or more Dense (Getting Higher Viscosity), and works as an added "Cushion" between moving parts to prevent shearing. In this group, you can find additives such like the "Lucas Transmission Fix" and many more.
Why is this very important?
Because if you pour an ATF Additive that thins the ATF and works as detergent, onto an Automatic Transmission's Fluid which also lubricates the Differential, and you drive long term like that, there will be a very high Risk of Breaking the Differential Gears due to improper Lubrication. Independently from the advantages that such additives could do to the Transmission; they simply are Not intended for the Differential, period.
However, you might pour the same ATF additive onto transmissions which does Not share the ATF for the Differential, in such case there is No Risk for the differential, because it is isolated from the ATF and has its own lubricant.
So, in case of Automatic Transmissions that shares the Same ATF for the Differential, you might pour those detergent ATF additives for short term use only, in example to do a chemical cleansing of the internals prior to do a complete ATF drain and then Refill with fresh ATF; but if you really need to Pour an ATF additive for long term use, on this kind of Transmissions that shares the ATF with the Differential, I highly recommend to chose wisely, from the ones that doesn't thin the ATF.
► Important Note: Not all the ATF in the market, has the same additive package nor are suitable for all the automatic transmissions; in fact, if you use the Wrong ATF, the Transmission might get damage, such like premature wear and shearing; Always follow the Manufacturer's recommendation on the Manual.
In my case, for my Wife's car which has a version of the 4EAT, I pour Valvoline's High Mileage ATF plus a quart of Lucas Transmission fix additive, and that combo makes the transmission to work smoothly and flawlessly; I do change all the Transmission ATF with said combo, on a yearly basis.
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