Found the book I was looking for. I knew it was somewhere in this mess! The 53 Preliminary Shop Manual for the "Internal oil passage power steering gear", AND "Powerflite transmission" says, "The Transmission and torque converter should be drained and refilled with fresh automatic transmission fluid (type A) every 20,000 miles." The manual has schematic's and repair procedures for the transmission & Power steering. If any one needs this (111 page) manual more than I do, contact me privately. Every thing I drive uses a clutch. Jim .......1939 Custom Imperial Limo C24