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Discussion Starter · #1 ·
Hello,

I have been having a problem with my JD2720 lift arms. I have owned the tractor for about 6 months and the lift arms had worked fine. One day I noticed the lift arms were in the full up position and would not come down, before, they would slowly drop over night. I have moved the Rock-Shaft Lever to the full up and down position and nothing happens. I have rotated the Rate-of-Drop adjustment knob to the fully open, half-open, and closed position and still nothing happens with the lift arms. I have read somewhere it was suggested the lift linkage could be binding; I carefully checked them, and everything seems to be moving freely. I haven't changed anything with the hydraulics since I have owned it.

Any suggestions would greatly appreciated.

Thanks,
Brian
 

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Your rate of drop knob has been turned. It is under the front of the seat. I don't remember which way it turns, but play with it until the arms drop. I just generally turn it all the way tight and then back off to what I want. Since I have rear implements that weight as much as 1750#, I have to keep mine fairly tight to keep them from "slamming" down.

Dave
 

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Brian, try bouncing up and down on the 3 pt with rate valve fully open. Just be careful! Unfortunate for me, my valve was froze. A friend took the valve out and freed it up. This was two years ago!
 

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Discussion Starter · #4 ·
Your rate of drop knob has been turned. It is under the front of the seat. I don't remember which way it turns, but play with it until the arms drop. I just generally turn it all the way tight and then back off to what I want. Since I have rear implements that weight as much as 1750#, I have to keep mine fairly tight to keep them from "slamming" down.

Dave
I will try adding more weight and opening the valve again. thanks!
 

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Discussion Starter · #5 ·
Brian, try bouncing up and down on the 3 pt with rate valve fully open. Just be careful! Unfortunate for me, my valve was froze. A friend took the valve out and freed it up. This was two years ago!
I will try that, I'm thinking the valve may be froze too. Thanks!
 

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Discussion Starter · #6 ·
I will try that, I'm thinking the valve may be froze too. Thanks!
to update my original posting, I still have not been able to use my lift arms. I have turned the rate of turn knob multiple times and it still won't move. I guess the next move will be to take the valve off and see if something is clogged.
 

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to update my original posting, I still have not been able to use my lift arms. I have turned the rate of turn knob multiple times and it still won't move. I guess the next move will be to take the valve off and see if something is clogged.
This might seem like a silly question but which way are you turning the knob? Turning CCW opens the valve and will allow the arms to lower. Turning CW will close the valve and prevent them from lowering. Are you turning it CCW until it won't turn anymore (don't force it of course)?
 
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This might seem like a silly question but which way are you turning the knob? Turning CCW opens the valve and will allow the arms to lower. Turning CW will close the valve and prevent them from lowering. Are you turning it CCW until it won't turn anymore (don't force it of course)?
While reading your post something occurred to me….

I don’t know how the knob is attached to the valve stem without going out to look, but could the knob be disconnected from the stem somehow? Is the knob turning but not the valve stem?
 

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While reading your post something occurred to me….

I don’t know how the knob is attached to the valve stem without going out to look, but could the knob be disconnected from the stem somehow? Is the knob turning but not the valve stem?
Here is the parts breakdown for the ROD knob on the 2720.

790956
 

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Here is the parts breakdown for the ROD knob on the 2720.

View attachment 790956
OK - so if the knob were loose it would be screwing in and out. Only takes a second to see if the lock nut is in place.

I always try to look at the simple stuff first before diving down a rabbit hole.
 

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OK - so if the knob were loose it would be screwing in and out. Only takes a second to see if the lock nut is in place.

I always try to look at the simple stuff first before diving down a rabbit hole.
Agree. That's why I mentioned to the OP about turning it CW and CCW until it stopped, without forcing it.
 
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I've been waiting to hear the OP found the solution. If it's not hydraulic, are there any mechanical causes? I know there is an optional lock-up for the mowing deck to secure it for transport. Could it be something like that?

I also have a 2720 and the 3PH lift function is one of the areas I haven't examined as it's all internal. What provides the lifting force on the arms?


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I also have a 2720 and the 3PH lift function is one of the areas I haven't examined as it's all internal. What provides the lifting force on the arms?
The basic operating premise is the same for all of Deere's SCUT/CUT machines. The 3pt arms function on a hydraulic cylinder that is internal to the transaxle case.

The hydraulic implement pump feeds the mid-SCV. That, in turn feeds the Power Beyond (if installed) and then goes on to the 3pt lift system. Your 3pt lift control lever has linkage that connects it to a hydraulic valve inside the transaxle case that drives the 3pt lift cylinder(s).
 
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I've been waiting to hear the OP found the solution. If it's not hydraulic, are there any mechanical causes? I know there is an optional lock-up for the mowing deck to secure it for transport. Could it be something like that?

I also have a 2720 and the 3PH lift function is one of the areas I haven't examined as it's all internal. What provides the lifting force on the arms?
On the illustration below, hydraulic force pushes on the piston (highlighted) which pushes on the rod with a ball on the end. There is a bell crank which couples to the splined shaft which rotates and raises the 3PH arms.

790977
 
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Discussion Starter · #15 ·
This might seem like a silly question but which way are you turning the knob? Turning CCW opens the valve and will allow the arms to lower. Turning CW will close the valve and prevent them from lowering. Are you turning it CCW until it won't turn anymore (don't force it of course)?
Yes, I have turned the valve both CW and CCW then backed off a little, each time still no movement with the lift arms.
"coaltrain, post: 3668630, member: 11397"]
While reading your post something occurred to me….

I don’t know how the knob is attached to the valve stem without going out to look, but could the knob be disconnected from the stem somehow? Is the knob turning but not the valve stem?
[/QUOTE] Sitting in the seat and turning the knob, and not actually seeing if the stem is turning too is a possibility, that would sure be a simple fix . The next time I go to my farm I will certainly check that out. T
I've been waiting to hear the OP found the solution. If it's not hydraulic, are there any mechanical causes? I know there is an optional lock-up for the mowing deck to secure it for transport. Could it be something like that?

I also have a 2720 and the 3PH lift function is one of the areas I haven't examined as it's all internal. What provides the lifting force on the arms?


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Thanks for the suggestions, I will certainly try out the suggestions. I have a feeling its something simple, just being overlooked. I will go over the knob very carefully to ensure it turning properly, the nest time I go to the farm. I will post the outcome.
 

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Don't recall all of the situation behind the issue I had once with my 2520 three point but if I recall either the joystick or aux hydraulics was stuck on and would not let the 3 pt drop. Another time I believe the seat belt buckle got caught and jammed the rockshaft.
 

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...hydraulic implement pump feeds the mid-SCV. That, in turn feeds the Power Beyond (if installed) and then goes on to the 3pt lift system...
Since the hydraulic system is a closed loop, could a disconnected / defective coupling on the Power Beyond section prevent flow to the 3PH cylinder?

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Since the hydraulic system is a closed loop, could a disconnected / defective coupling on the Power Beyond section prevent flow to the 3PH cylinder?
Yes, in theory at least, it certainly could. If hydraulic fluid can't pass through the PB coupling then it would never get to the rockshaft.

That should be easily noticeable though. If the system is running and the PB connector is blocked, the hydraulic system has to be bled off somewhere. The pump is pumping fluid that normally passes through the PB couplers and it has to go somewhere. So if the PB connectors are disconnected or blocked the mid SCV will go into relief right at start up and allow the system to bleed off. You'd hear it whining all the time. Operating the joystick to raise/lower a loader may allow the whining to stop for a few seconds (That'd be a quick way to check.)
 
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Just another thought on the subject…

I’ve seen (read about) 3 point hitches being stuck all the way up. What happens sometimes is that they actually seize in the full up position.

No real way to diagnose without going inside the case - but it some cases folks have hooked a chain around a tree and to the hitch and gave it a jerk to free it.

If it were my tractor this would scare me….but it all else failed I would probably try a couple “light” jerks to see what happened. Of course you would want the control lever in the down position. And be very cautious of doing too much of a wheelie….
 
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