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Modern Tractor Discussion Board Re: used 100 h.p. tractor purchase [ Expand ] [ View Replies ] [ Add a Reply ] [ Return to Forum ] Posted by RodInNS on July 16, 2009 at 05:32:18 from (216.118.158.123): In Reply to: Re: used 100 h.p. tractor purchase posted by Tx Jim on July 16, 2009 at 04:13:35: The Ford's of that day were technically open center systems except that they used CCLS valves... so in that sense they were closed center WITH load sensing. The vintage Deere's used a radial piston pump... as you know. When there was no demand they destroked at high stand-by, always maintaining system pressure. IF there was a leak anywhere, the pump would go to stroke and try to plug the hole... The newer systems are often called CCLS. They are more properly called PFC or Pressure Flow Compensated. They use the same remote valves as the Ford's did... which is to say that they are closed center with load sensing... and the same as the Ford's, if you don't activate a valve, there is no flow to the valve. The system is at rest. The main difference is that this system uses a variable displacement pump like the old Deere's in combination with a pressure compensated flow control. Wheras the Deere would stroke with a pressure drop, these systems have their stroke controlled by the PFC valve. When a remote is activated, that creates a pilot flow (demand) signal to the PFC valve which then directs oil to the stroke control on the pump. The more demand, the more it strokes the pump. It can run at high standby like the old Deere's if you tie the remote off so it maintains demand... but the main difference is that when you kick the remote to neutral, the pilot flow is cut off, demand ceases and the pump again returns to a destroked position. It is supposed to be a more efficient system in that it allows thigns to relax and lower the power requirement along with reducing stress on the system. The main failing I've seen with that generation of Deere's that existed around here was high pressure leaks from that system... somethign that's more or less removed in the PFC system. That's not to condemn the old system. It's been around on those tractors for the best part of 50 years, but time has overtaken it. Deere went to PFC about 20 years ago if I'm not mistaken... Rod Replies: Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Optional Video Title: Optional Video URL: Advanced Posting Options Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.   Advanced Posting Tools   Upload Photo  Select Gallery Photo  Return to Post