JD 4720 Hydraulic Failure

   / JD 4720 Hydraulic Failure #1  

blackfalcon

New member
Joined
Jan 5, 2009
Messages
11
Hey guys. I have a Deere 4720 less then a year old with about 265hrs on it. I haven't drove it much when it was cold. I briefly drove it the other morning when it was around 30 out and I noticed hydraulics seemed to be running a little slow/sluggish. I went to drive it this pm and spent approximately 10 minutes on it. I noticed the hydraulics were running slightly sluggish again, almost like if the fluid was low (which is what happens on my 2720 when its low). I went for a second scoop of loose dirt, the tractor stalled out. I restarted it, and was unable to move bucket, steer, go back and forth etc. etc. Basically complete hydraulic failure. I check fluid and it was right at the top of its range etc. Am I missing something simple that would cause all the hydraulics to fail? Is there anything I should check before calling the dealership.
 
   / JD 4720 Hydraulic Failure #2  
The suction screen would seem most likely.
 
   / JD 4720 Hydraulic Failure #3  
Suction screen is a good idea. Have the filters been recently changed?

Maybe the relief failed and is letting all fluid bypass?
 
   / JD 4720 Hydraulic Failure #4  
IMO no way could this be a dirty oil issue-with those kind of hours I would be standing on the dealer's desk right now-not your problem-that is why we pay the big bucks for that green paint!
 
   / JD 4720 Hydraulic Failure #5  
I would definitely focus on the suction side of things...that's the only common denominator. There are 2 separate pumps (3 counting the hydrostat), so 2 separate relief valves. The power steering pump supplies charge flow to the hydrostat pump. There is a short chunk of suction hose near the pump set also, you may want to look at that too. I suppose that the pump drive coupling could have sheared, but I hope for a suction screen or filter.
I would let the dealer handle it.
 
   / JD 4720 Hydraulic Failure
  • Thread Starter
#6  
The pump drive shaft sheered off from what I was told by the JD dealership. They ordered the part and will be back in business Friday.
 
   / JD 4720 Hydraulic Failure #8  
Was it a manufacturing defect, or something that caused it, or just bad luck?
 
   / JD 4720 Hydraulic Failure #9  
I am not seeing how one pump caused total hyd failure.

A dead implement pump would not affect the transmission.

If it has a steering pump, it should still work.
 
   / JD 4720 Hydraulic Failure #10  
The pump drive shaft sheered off from what I was told by the JD dealership. They ordered the part and will be back in business Friday.
Glad to see ya up and running
 

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