I have a 1984 Catalina 27 with the M-18 Universal Diesel. My manual recommends Dextron II for the Hurth HBW-50 transmission...I think they meant Dexron II. Dexron is a GM spec and trade name. Dexron II is no longer licensed by GM and it is now replaced with Dexron VI. The info I found said Dexron VI is backward compatible and should work in any application that required an earlier type of ATF. Has anyone replaced their transmisson fluid with Dexron VI?
