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New 790 -- Less HP

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deeremd
Join Date: Jul 2003
Posts: 18 maryland
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2003-02-24          49892

I recently purchased a new 790 w/ 419 FEL which was delivered over the weekend. However, looking at the spec sheets that came with the tractor, it appears that the new 790s have less HP than when I looked at them a couple years ago. (I think I remember them having 30 GHP/25 PTO HP but my manual says it has only 23 PTO HP?? The gross HP is also listed as less than 30 in the manual.) Does anyone know if something has changed in the 790 line? Could it be an error in the manual?


Also, has anybody compared the specs on the new 419 FEL versus the 70? Just going by memory, it appears that the 419's lifting capacity is less (according to the 419 manual)??


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DRankin
Join Date: Jan 2000
Posts: 5116 Northern Nevada
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2003-02-24          49894

My govt spec book lists three numbers.

Engine gross: 30 HP
Engine net: 27 HP
PTO: 25 HP

Many Deere owners are discovering errors in their manuals and specs. The problem really is that you don't know which set of numbers to believe.

You can e-mail Deere customer service and unlike Kubota, they will answer you. ....

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New 790 -- Less HP

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-02-25          49949

Aside from just plain errors in manuals, specs have been a problem for a long while. The Nebraska Tractor Tests were created by state legislation decades ago because farmers couldn't get a good sense of what tractors could do or compare different manufacturers from their specs. The test is part of the University of Nebraska and is what amounts to an independent testing laboratory for tractors. Too bad it's limited to farm tractors.

Specs from manufacturers are part engineering, part legal and part advertising. If the thinking in any of those areas changes, the specs can change and it may have little to do with performance of the tractor.

On the engineering side, there often are re-engineering and design changes within production models. Some of these things can affect HP. Some genuine engineering issues can be addressed and result in production changes that affect HP.

Here's a completely hypothetical example of the sorts of situations that can occur. Let's say the JD marketing people decided to position the 790 as having a lot of HP for the size and price. So, the engineering design was for a governor that came close to max fuel delivery. After the tractor went into production, field statistics indicated that there were over-heating problems doing heavy work on hot days, so a production change backed off on the fuel delivery a bit. New specs would indicate lower HP ratings.

In contacting JD about their varying specs, it also would be good to find out if there were any production changes--governor calibration in particular.


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MRETHICS
Join Date: Jul 2003
Posts: 190 Star City, Indiana
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2003-02-25          50025

Specs are unruly creatures. They are recited, repeated, replaced, required, readjusted.... ad nausium.

Like the old adage "Democracy is in note in the voteing, it's in the counting" specs are measured in different ways, by different people.

The Nebraska Tests set things straight, they should be required on compacts as well. I think this would be a better nation for it.


As fo the 419 vs 70 loader, I recomend useing the "breakout" as a way to compare strength. Lift capacity is derived by a strength vs stabilty kinda thing.



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CallMeBob
Join Date: Jul 2003
Posts: 11 Southwest Missouri
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2003-02-25          50034

What exactly is "breakout force" and what happens when you reach it?
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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-02-26          50079

I'm not 100% on the exact definition but it's along the lines of the force a hoe curl can apply measured at the bucket teeth. I think hoe stick hydraulics also have breakout specs as do loader loaders.

I interpret them as measures of how strongly something will dig or move a static load. I guess it's called breakout because you apply force and a load either moves or it doesn't.

A hoe can't exceed its breakout force specs because the hydraulics stall because the relief valve opens. That's one of the nice things about hydraulics. As power sources, they don't overload, burnout or break, but they shouldn't be operated for prolonged periods with a relief valve open.
....

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DeereTech
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2003-02-26          50081

I repair these tractors everyday as well as prep for delivery, what ever HP Deere said they make on the PTO they will make. We dyno everyone before it leaves for engine breakin so I know what the HP #s are.
Just a note ........Deere says that ALL compacts need run in on a dyno perdelivery to make sure the engines are broke in, which is not a problem for us as we are a AG dealer and the dyno is a must have but not very many CP dealers have one.
I just came back from a Engine school and Deere talked a LOT about these tractors not being broke in properly on delivery.
Your tractor may not be up to HP if it has not been broke in per Deere instructions. ....

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Deere Tech
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2003-02-26          50083

One more thing I might add.........Hp #s are a sales gimick as it means nothing to me in checking out a horse power problem on you tractor.
If you bring your tractor back to me with a HP complaint we will dyno it but not for HP #s but to plot its torque curve and torque rise.........They have specs for this and they are in the tech manual. If torque is there you will have horse power.........Rob ....

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CallMeBob
Join Date: Jul 2003
Posts: 11 Southwest Missouri
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2003-02-26          50116

Thanks to TomG for answering my question on breakout force.
Bob ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-02-27          50163


Deere Tech mentioned toque-rise. Percent torque-rise is a stat that's contained in the Nebraska Farm test results but I've never heard of it in any of the factory specs for compacts.

Some years back NH crowed that one of their farm tractors came out top of the heap in one of the Test results and they seemed very proud of the percent torque-rise. I've never been certain of the exact definition and I'm curious.
....

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17ACRES
Join Date: Jul 2003
Posts: 15 Lake Stevens, WA.
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2003-02-27          50166

Deere Tech/Anyone,

In your previous post you spoke of "proper breakin". I just took delivery of a new JD4510 from a large AG dealer. I don't remember seeing a dyno in their shop, so lets say that the engine was not broke in on the dyno. What is the best method for tractor diesel engine break-in after delivery? I looked for guidance from the JD manual and I didn't find one word about engine break-in. That would lead me to think that normal usage is sufficient?? ....

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deeremd
Join Date: Jul 2003
Posts: 18 maryland
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2003-02-27          50175

FYI: Here is the information I received from Deere:

"Thank you for contacting our website.
Here are the specifications from the latest operator's manual for the 790:
Gross HP at 2600 rpm = 26.2
PTO HP =23.6 estimated.
The 419 loader lift capacity is as you see in the specifications section of your owners manual for the loader and it is less than the 70 loader as you have indicated."

I find it disturbing that Deere could have produced a new model year tractor and replacement FEL with less capability than the older style (assuming that this message actually confirms what's printed in the manuals). Does this make sense to anyone??
....

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DavesTractor
Join Date: Jul 2003
Posts: 148 Red Bluff, California
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2003-02-27          50179

Not that this will help much, but I had a JD 770 a couple years ago and I think it had 25.9 Engine HP. Does anybody know if the 770 and 790 run the same displacement Yanmar engine? The tractors look the same. I am wondering if much changed.

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Gunfighter
Join Date: Jul 2003
Posts: 23 West Michigan
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2003-02-27          50220

I remember reading something awhile back where the EPA will expand it's clean air requirements to tractor. The JD 790 uses a direct injection engine which is more efficient but runs a little dirtier then a indirect engine.

I have a 2001 JD 790 an the owners manual show it to be 30 hp engine, 25 hp PTO.

Congratulation, even with the reduced hp, I think you made a good choice on tractors... ....

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plots1
Join Date: Jul 2003
Posts: 563 mo
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2003-03-03          50455

just got email from JD web that states 790 has exactly what there web site shows 30 gross hp 25 pto hp. WHO DO WE BELIEVE HERE????????? SEEMS NO ONE REALLY KNOWS! ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-03-04          50472

Dave:

I come up with a 3/91.3 at 30 engine HP for a 790 from the JD site and a 3/83.1 at 24 engine HP for a 770 from tractortips. Seems a good bet that they're different engines. ....

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