JD 448 backhoe problem

   / JD 448 backhoe problem #1  

doppler46

New member
Joined
Nov 15, 2010
Messages
14
Location
Central Texas
Tractor
JD 4310 JD448 backhoe attachment, Farm Trac 60, John Deere 5055
I have a JD 4310 with the JD 448 Backhoe attachment. Everything except the dipper works good. The dipper goes up and will lift but when I lower it just free falls slowly and will not apply downward pressure. It is not applying a load on the motor or hydraulics. Any suggestions?? Thanks!
 
   / JD 448 backhoe problem
  • Thread Starter
#3  
Not the boom. Based off the picture you posted it is the stick. My manual calls it a dipper. I tried just partially moving it and all the way with the sane results. When I lift it it puts a load on the tractor like normal. When I go to lower it just free falls and will not apply any down pressure. I asked the dealer today and he said swap the cylinder with te boom cylinder and see if I have the same fault. At least he did tell me he has not had many problems with the backhoe in the past. I cannot see it being a cylinder problem. There are no leaks and I do not hear fluid rushing as if it is bypassing some where in it. I am thinking valve body but I have never taken one apart.
 
   / JD 448 backhoe problem
  • Thread Starter
#4  
Anyone have the hydraulic Schematic for the backhoe?
 
   / JD 448 backhoe problem #6  
Did you buy used or new? If new -- call dealer.

If used, you probably have a blown out seal on the dipper stick cylinder or a worn control valve or the bypass on that circuit is stuck open.
 
   / JD 448 backhoe problem
  • Thread Starter
#7  
I bought it new 3 years ago. I have dug hundreds of cedar stumps with. I think I am going to swap the lines with the spool valve next to the one that is not working and see if the problem changes. The dealer said to swap the boom cylinder with the dipper cylinder. I think it will be easier the other way. Thanks!
 
   / JD 448 backhoe problem #8  
I have seen a hundred cylinder problems for every one valve problem. I would bet it's a blown piston seal.
 
   / JD 448 backhoe problem
  • Thread Starter
#9  
Okay tonight I swapped the hoses on the dipper cylinder to see if the fault would change. When I swapped the lines on the cylinder I had down pressure but it would not lift up. So the fault did change. So it is not the cylinder. I then decided to take the spool valve shaft out and see if there was any damage. The shaft looked good and so did the valve body. I put it back togeather and still the same problem it would not appy down pressure. I took the lower hose off the cylinder and held it in a bucket and started the tractor. With out activating the lever I had a steady flow of fluid coming out of the hose. When I activate the lever the same amout of fluid came out and I could put my finger over it and stop the flow. I then took the other line off and with the tractor runnin there was no fluid flowing. When I activated the lever it had good strong pressure.
So the question now is can it be the pressure relief valve that is causing the problem? Has anyone taken the pressure relief valve apart before? I did not think so since it should be part of the lift portion of the dipper also. But I am doing this by trial and error. Any suggestions??
 
   / JD 448 backhoe problem #10  
Doppler46:

First, I am not a JD guy and only an amateur at hydraulics. But I have a couple of suggestions:
1.) Post this on the Hydraulics board, I think you will find more help there.
2.) If the earlier refernced diagram is a diagram of the boom, dipper or sick, and bucket curl parts of your valve (not sure what happened to swing) I would be mighty suspicious of the load check valves, as opposed to the relief valve. If the relief valve were bad, normally one for the entire valve body, if seems like all the valves in the body would have a problem. But the load checks are, in essence, relief valves for individual cylinders . I suspect, if you have load checks, the one for the dipper cylinder is either stuck or has a broken spring in it. Now, in terms of taking it apart, diagnosing and fixing it, this is one place the folks over on the hydraulics page could really help.

Hope this helps. Best of luck.
 

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