ATF is a 20 weight hydraulic oil. No way will I ever put it in my Sportster trans calling for a 50 weight.

The main requirements of an ATF are thermal stability and friction modification (lubrication), with some anti-wear additive for the Sun, lock-up, and Planetary Gears, and of course, the needle/pin bearings. Add about 0.05% of anti-foamants (siloxanes) and some red dye for leak identification, and you have an special Hydraulic Oil called, 'ATF.' The formulator will tweak the additive package for each base oil type (group) or mixes of base oils.


Here is the chemistry for an ATF such as Dexron III:
(Average additive concentration by wt.% taken from seven (7) different additive packages)

Phosphorous - 0.3% AW additive
Zinc - 0.23% AW additive, anti-oxidant as ZDDP
Nitrogen - 0.9% AW additive
Boron - 0.16% Detergent and AW additive
Calcium - 0.05% Detergent/Dispersant, tbn base chemistry
Magnesium - 0.05% Detergent and base chemistry
Sulfur - 0.55% FM and AW
Barium - various% used as particlate control

In the newer ATF oils of Group II-III, added esters of lineoleic esters, TMP polyol ester, and PE polyol ester, and other carboxylic esters, act as FM additives. The Additives phosphorous, sulfur, and boron are usually added in the form of esters when formulated with the base oil. For fully synthetic oils, the PAO and polyol ester bases are the main Friction Modifiers.

The Mercon chemistries usually have higher concentrations of nitrogen and phosphorous.

Boron and Phosphorous act as the main AW additives if the ZDDP is low or non-existent.

Calcium and magnesium are, of course, base metals and provide the "basicity" to keep acids in check and provide the starting tbn.

It has been found that ZDDP will turn the red-dyed ATF brown through oxidation, so some formulators have reduced or taken out the ZDDP and replaced it with other AW additives.

 

I run Mobil 1 syn ATF with 3 ounces of Lubeguard highly friction modified ATF supplement.

Smooth shifting, very little klunk, zero issues.

'15 Limited.

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