In the 1950s, 1960s, and 1970s, ATF contained
whale oil as a
friction modifier. But since whale oil would break down at higher temperatures, cars produced in the 1970s and later would not be able to use whale oil because of the higher
engine coolant temperatures employed to reduce emissions and save fuel. A moratorium on whale oil at that time prevented the continued production of older ATF such as the original
DEXRON formulation (Type B), and the Type A which preceded it. Vintage Chrysler products (Dodge, Plymouth, etc.) used Type A fluid, which is generally difficult to obtain now.
It turns out that Type A was basically a nearly 50/50 mix of Type F (Ford) and Dexron (GM),[
citation needed] so if you have a pre-1990 Chrysler vehicle, you can mix Type F and Dexron to get a near-match for type A.
General Motors began marketing Dexron II Type C and later Dexron II Type D to replace the fluids which were made from whale oil.
[10]
Through the late 1970s, Ford transmissions were factory filled with a fluid identified as ESW M2C33-F. To provide a fluid that would be available to the general public for service fill, oil companies and other than factory fill suppliers were allowed to develop fluids meeting the ESW M2C33-F specification and market these fluids under their own brand names but identified as Type F.
