I have a 909 and 743. The 909 controls are open spool, allowing continuous flow from the aux hydraulics. Aren't all aux hyd continuous flow once you enable them by pushing the lever to the side? On a 643, some things come to mind. 1. the 909 is bloody heavy. On my 743, I find it isn't easy to move it around when I'm not on flat ground. On a 643, you will be even more front heavy. 2. the 909 can drag my 743 around easily when i'm into hard pack clay or hit boulders. a 643 will be tossed around even more 3. the 907 was the "preferred" backhoe for the 643, which says it also fits on a 743, so a 909 should also physically fit onto a 643. Newer version was 607 (and 709 for 7xx series). http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=57528 http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=59586 so, I would say you can use it, but you might not find it any fun to try to move it around or use it.
