I just installed PS in a 1949 Packard. The modified system uses a 1953 Chrysler 6V Generator that has a PS Pump attached to the back of it and the other end of the hoses is a Monroe external hydraulic actuator that is installed in lieu of the center link and this is the unit that the 1955 Packard used for PS. The Chrysler manual specified SAE-10W however the Packard manual specifies "Ultramatic" fluid (also called Type A fluid however some say Type F can be used as a replacement). I used regular old PS Fluid from Autozone and the system makes a humming sound when the power assist is in action. Does anyone know what kind of fluid I should use???