LoadMatch and PTO Operation

Cocre · Jul 4, 2009

Odd behavior or normal? I have 2006 JD 3320 eHydro with a 300x loader, LoadMatch is always on (mostly), around 350 hours. After bush hogging for a while if I drop the engine RPM below 1700 the tractor loses almost all forward speed. It just creeps. Anything above 1700 RPM and the tractor is back to normal. PTO on or off does not matter from that point on, below 1700 and creeps, above and zoom. The fluids are fine, letting the tractor cool (it is never hot) for an hour does nothing, still the same. Turn the LoadMatch off and the tractor is back to normal, turn the LoadMatch on and the behavior returns. My unit has the switch on the dash to facilitate this.

I do not know what I do to "fix" the issue. I have turned the tractor off and on, off and on with the LoadMatch disengaged, off engaged on disengaged. At some point it just resets something and it goes back to normal. I thought I had it figured out, but the last time this happened, nothing I did fixed it. The next morning everything was back to normal. Perhaps the hydro oil gets too warm (it has been near 100 everyday this week) and thins out to the point that the LoadMatch thinks it needs to do whatever it does when the RPM drops below 1700. Yet with the LM off, the tractor runs just fine, or it runs with what I deem to be expected behavior at all RPMs.

The LoadMatch works great under normal circumstances. It really does help when pushing into a pile of dirt, or when climbing a long steep hill with a heavy load. I am just curious about the bush hogging behavior. Perhaps I should turn the LM off when hogging.

Any comments are welcomed.

mfreund · Jul 5, 2009

I don't care for the loadmatch and I leave it off all the time. IMO. I figure I am smart enough to let off the hydro pedal if it bogs down.

sunnyside360 · Jul 5, 2009

My 3720 and 4320 both have Load Match. I cannot distinguish the difference in operation with LM on or off unless the engine is heavily loaded regardless of temperature and RPM's.

mfreund · Jul 7, 2009

LoadMatch works OK when you are PTO work but I don't care for it any other time so I never turn it on.

ddivinia · Jul 13, 2009

I don't know what to say on this topic.

On my 4720 open station I only had the load match when I was moving dirt in the bucket up a grade. It was kick in and keep going.

I have never seen it engage when running a mower.

I was punching holes for some new corrals with my 4520. The ground was wet enough that the auger was really digging in - I could hear the turbo kicking in big time. I used that as my gauge to pull it back out.

Not sure if any of that was helpful,
D.

Cocre · Sep 8, 2009

An update to this problem.

The issue had nothing to do with the operation of the PTO, it was more time or heat related. I think the additional summer heat may have made just enough change in the throttle position sensor voltage values to throw the LoadMatch calculations off.

Another 3x20 owner notified me via email that they too had this very problem. They had John Deere look at it and Deere fixed it by replacing the throttle position sensor, an easy fix.

Rather than haul my 3320 to Big John I took a look at the throttle position sensor myself, made some adjustments, and think I have resolved my issue. Adjusting or replacing the sensor is easy if you have the technical reference manual (I do).

The sensor is supposed to read between 0.6 and 1.2 volts at the slow idle position and between 2.0 and 3.7 volts more than the slow values at high idle position. You can read the voltages right off the tractor display if you know how to get to the diagnostics. My voltages were 1.1 and 2.9, so I was at the high end of OK on the low idle position and only 1.8 volts higher at the high idle position.

The sensor was leaning a bit to the right so I loosened the bolts (8mm wrenches) and straighten it up by slightly rotating it counter clockwise. My voltages then read 1.2 and 3.2, just within tolerance. I cranked the tractor up, and the thing would not move at all with LoadMatch on until I got around 2100 RPM, this was way worse than before. So I shut the tractor off and rotated the sensor clockwise beyond its original position. The voltages were 0.4 and 2.1. Not within specs, but I cranked the tractor, turned on LoadMatch and headed toward the dirt pile. It would move forward at 900 RPM with LoadMatch on, something it had not done in sometime, but when attacking the dirt pile (2100 RPM) the tractor let me know that even though the LoadMatch switch was on, that the voltages were off enough to make the tractor grunt a bit more than when LoadMatch is right.

So I shut the tractor down again and backed the sensor back to just right of its original position. The voltages read 0.8 and 2.6, still a bit off spec on the high end, but the tractor ran perfect, LoadMatch worked as I expected. Forward movement at low RPMs and it would unload the drive train when pushing too hard.

My conclusion is that the slow idle position voltage has a great impact on the LoadMatch performance. I think my sensor is just off spec, so I may end up replacing it eventually (cost around $90). I guess time will tell.

Hope this helps any others that may have this issue arise.

Cocre