Useful specification information and has exact dates for all changes to the 7x from 1984 through current. This information should put to bed many things that are "unknown" or consistently discussed incorrectly here. The information here is directly from the proverbial "horse's mouth." First portion is the Chief Engineer's design concepts as well as working parameters for the development of the next generation 40 series (which is basically what the 70 series was when it was introduced). The information below includes all heavy duty as well as medium/light duty 7x models for the JDM as well as export markets.