They said ATF in later years as a "Band Aid" remedy to user complaints in cold weather of hard shifts. Of course: gear oil thickens in the cold, until driven only a few miles, then works fine. These weren't designed by Chrysler to "user friendly", but rather to transfer, and withstand, heavy loads They (Chrysler) weren't concerned about long-term (high mileage) effects (wear & tear). Sure: racing OK. Less frictional losses. But any geared power transfer unit (a833, rear axle) needs heavy gear oil for best lubrication properties.