Go Bottomhydraulic lift on JD4400
 | James
Join Date: Posts: 1 
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2001-06-16 29341
I have a DEERE 4400 hst with FEL and 5' rotary mower. When I lift the mower the lift will pulsate. I mean it will lift all the way up with no problem but will then drop about an inch then lift then drop then lift. Does not matter what the engine rpm is also have no problem with the FEL. the FEL will hold any position I put it in with no pulsation. Fluid level is fine. Great machine anyone else notice this problem.
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Add Photohydraulic lift on JD4400
 | dsg
Join Date: Jun 1999 Posts: 528 Franklin, Maine 
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2001-06-16 29343
James, the answer is yes. JD has been having problems with the seals in the rockshaft. I have a 4700 and have had the seals replaced (under warranty)at about 400 hrs. and I think I'm going to have to have it done again now with 585 hrs. According to the Service Manager the 3pt hitch is suppose to leak down with a load on it when the engine is off as long as the 3pt valve that controls the speed of the 3pt drop is not closed. But if the valve is closed it should not drop and also it should drop with the valve open and the engine running. David ....
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Add Photohydraulic lift on JD4400
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2001-06-17 29350
DSG's comments specific to JD. In general, various leaking valve seats and o-rings in a 3ph will cause a hitch to cycle up and down, which probably is why the 3ph cycles and the loader doesn't leak down. It's likely that the 3ph isn't holding oil under load, it leaks down to where the position control goes into lift mode. If the tractor is near to a scheduled hydraulic oil/filter change, you might change oil. Small chance, but it might help. Various small hydraulic oddities disappeared after I changed oil. ....
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Add Photohydraulic lift on JD4400
| dsg
Join Date: Jun 1999 Posts: 528 Franklin, Maine
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2001-06-17 29354
My misstake, At the end of my reply it should read- (the 3pt SHOULDN'T drop with the valve open and the engine running) sorry. David ....
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Add Photohydraulic lift on JD4400
| DoctorDeere
Join Date: Posts: 1
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2001-07-01 29751
Check the line fitting where the oil line connects to the lift valve housing. I believe you'll find that the small screen in the fitting has come loose and lodged in the lift valve spool. I've replaced a dozen lift valves for this reason (the screen becoming lodged will score the valve spool, rendering it useless). The symptoms are just as you describe.
The lift valve is located under the range select cover on the left side. Fender removal is required. ....
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Add Photohydraulic lift on JD4400
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-07-02 29758
Dr.: I'm always interested in design issues. I never thought of a screen in the 3ph high-pressure line. At first, I thought 'Why?' After all, the oil runs through a full-flow filter just before the pump. I guess the answer is that the auxiliary system is ahead of the 3ph, and junk could get in the oil through aux system quick-connects of from the lines of any implement with hydraulics. I suppose it's a lesson, especially for those of us who don't have screens, to make sure fittings are clean before connecting them. there may be a lesson for Deere as well. If you have replaced dozens of screens yourself, I’m surprised Deere hasn't come up with a replacement that doesn't come loose. The number of failures world-wide must be huge. Maybe dealers should be bugged, and then dealers might bug their manufacturer reps. ....
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Add Photohydraulic lift on JD4400
| DoctorDeere
Join Date: Posts: 1
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2001-07-02 29775
Actualy, it's the fitting itself (with screen) as well as the lift valve that must be changed. What happens is this: The screen catches some debris, which causes a partial restriction at the screen. The resulting pressure differential on the upstream and downstream sides of the fitting literaly blows the screen out of the fitting and into the lift valve. Then the operation of the lift valve causes the stainless steel screen to score the lift valve spool. ....
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Add Photohydraulic lift on JD4400
| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-07-03 29780
Yes, that's the way I understood your comment. The spool gets damaged. It just seems ironic that a device put in, as I understand, to protect the 3ph from junk accidentally introduced during implement swapping may cause as much damage as the problem it's intended to prevent. ....
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