2001 7.3 245,000 miles. batteries fully charged and load test very well, connections clean and tight, alternator replaced 2 years ago and is producing 14 volts while running. truck starts okay initially but if I back it out of the garage and shut it off it will not restart, cranks slow and acts like batteries are dead, quick boost with another vehicle, less than 5 minutes connected and it starts right up again and is okay if I drive it any distance. also seems like batteries are drained after a day or so sitting. Kind of stumped on this one and don't want to start throwing money at parts I don't need. I believe it's the original starter, the truck was from the south (Georgia) so I don't think corroded connections are an issue. Any help is greatly appreciated.