Hydrostatic Issue - Dealer says replace - About $8000

[Wes Crawford]

Background: 2004 JD 4410 Hydro, 1100 hours.

A few weeks ago I used my tractor with no issues. Worked fine. The next time I started the tractor, I got some serious movement hesitation with the hydro. Push the forward pedal and the tractor would jerk forward a few feet, hesitate for several seconds, then jerk forward again a few feet. No continuous movement forward. It was the same in reverse. I let it warm up for 20 - 30 minutes and then it worked much better with an occasional hesitation that went away when I started brush hogging a 2 acre field. The tractor ran fine the rest of the day and until I put it away. By the way, the loader worked as well as always and the PTO obviously worked. Last week I got started the tractor and the hesitation and jerky movement was back. This time I let it warm up and it got better, but still some occasional hesitation. I then went into the woods and brush hogged my logging roads and trails. It wasn't perfect, but it more or less worked. I thought it might need a clean filter, screen, and oil, so I changed the filter, oil, and cleaned the screen the next day. When I started it up the next time, the hesitation and jerky movement was even worse. The tractor would hardly move 10 feet in a minute.

So, I called the dealer yesterday and had them pick it up. They analyzed it per JD requirements and found that the internal pressure was only about 1000 whereas they said it should be about 5400. JD's recommended solution is to replace the hydro completely. They said they didn't have the capability to repair the pump assembly. So, they said the cost of a new hydro is $4350. Labor to replace would be about $3000 and miscellaneous seals, fluid, etc might be another $1000.

A new dealer bought out the one I originally purchased the tractor from in 2004. The techs are competent I imagine, however, I'd feel better about the diagnosis if an older guy who worked on the tractor before was still there. Can't hydro's be repaired instead of replacing the entire housing, gears, pump, etc? Does anyone have any words of wisdom or suggestions for me? Thanks!

 

[Deere Dude]

After changing my trans oil I can count on sluggish and erratic movement for a few weeks. Maybe to work all the air out, I don't know.

Later I found it was now working adequately after I changed the oil so I asked around on this forum as to suggestion. I knew the oil level was full, but then I rechecked it and found it was 1/2" below full. So I got a quart of Lo Vis Hygard and dumped it it. To my surprise it actually took a whole gallon from that point on the dipstick.

I would verify the level every day before using it and make sure it is the right oil. An $8000 pump wold make me squeamish and would check any alternative before that happens.

 

[kennyd]

I think I'd try the engine speed sensor, they are about $70 and can cause issues with the eHydro operation if the signal is not clean.

 

[texasranger556]

I don't know how the "E" stuff plays into it but to me it sounds like low charge pressure. My 4400 was acting similar when I bought it although not nearly as bad as you described. We lapped the valve plates in the transmission, put it all back together and it did the exact same thing (the plates weren't very bad at all, 500 hours of use). The power steering pump is also used to charge the transmission, there is a regulator valve that holds 150 psi or so into the transmission. It is up next to the hydro filter on the front of the transmission. When we removed it the spring was sort of jammed. Took the spring and poppet type thing out, put it back in and it's been good ever since. In retrospect we could have saved a whole day of work, but in the end the transmission is like new now.

Ask them what the charge pressure was when they measured it. If you don't have good charge pressure, I don't believe you can trust the high pressure readings.

 

[Tx Jim]

5400 psi factory setting for hyd pressure sounds very high to me.

 

[texasranger556]

6000 is what mine calls for, 200 for charge pressure. Here is the thread I started a couple years ago.

http://www.tractorbynet.com/forums/showthread.php?t=344133

 

[texasranger556]

Regarding your question about repair, a lot of dealers won't do it because it's a lot of labor splitting the tractor and getting the hydro out. If they screw up or mis-diagnose then they end up eating the cost of doing it again, so they just quote a new transmission to be safe. Another dealer or independent shop may be willing to fix rather than replace.

When I was looking at repairing mine, the parts diagrams showed you can order individual components from Deere. I've seen HST parts available from Kubota too. On the ones I've seen, it's usually the valve plates that show the most wear due to cavitation, contamination, oil overheat/breakdown. Sometimes just wear. This lets oil leak between the ports instead of driving the motor. You can lap the plates back smooth and the only cost is labor. Or buy new plates if available. However this type of failure is normally gradual degradation, not immediate like you describe.

The pistons/slippers can also go bad which usually means buying the whole rotating assembly because the pistons I'm told are precision ground to fit the cylinder block so they sell as a set which is obviously more money.

In your case if the charge pressure checks out ok, then due to the rapid onset of issues I'd lean more toward a slipper failure. Once one fails it can score up the swash plate face and damage the rest of them pretty quick. If you run long enough the metallic particles can ruin the motor too.

I don't have any experience with the e-hydros as far as a control/sensor problem that could explain the behavior you experienced.

Dfkrug is also experienced with hydro transmissions, so he may add comment/corrections to what I've said. If you do end up needing a new transmission I would be interested in doing a teardown on the old one and post the details here. I periodically visit in-laws near Indianapolis.

 

[dfkrug]

Dfkrug is also experienced with hydro transmissions, so he may add comment/corrections to what I've said. If you do
end up needing a new transmission I would be interested in doing a teardown on the old one and post the details
here. I periodically visit in-laws near Indianapolis.

All good suggestions.

A proper diagnosis at the dealer is to check fwd and rev relief pressure, AFTER verifying the charge pressure.

I do not know the e-Hydros either, but Deere HST parts are available so buying the whole thing is not
necessary.

I do hope that this unit gets properly diagnosed and a post-mortem performed and posted on TBN. I would do
it too, TEXAS.

Let's hope it is an e-Hydro component, or a bad flow divider on the PS pump.

 

[Wes Crawford]

Everyone, Thanks for the comments and analysis. I appreciate it. I'm having the dealer return my tractor to my tree farm. I called another dealer and explained the problem and the pressures to them and they weren't certain that a new transmission was needed. They have a technician who has 40+ years of experience and they are going to consult with him when he returns from vacation next week. I believe I'll have them pick it up so they can do a thorough diagnosis of the problem. They are farther from my farm, so I'll have to pay a $50 RT delivery and return, but that will be worth it. I'll see what result I get next week and then post what I find. I appreciate the offer to look at it when you are in Indiana, texasranger556.

 

[RoyJackson]

Please do keep us up to date on what the tech determines!