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Charles
Join Date: Apr 2004
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2000-11-11          21405

Hello everyone. Took delivery of my 790 on tuesday. I love it so far. (only have 1 hour on it,so time will tell) Anyway,i have a question.Should a 70 loader be able to pick the front wheels up off the ground?Also,is a hydraulic center link the only way to get "down pressure" on the hitch? It sure would be nice to have some for grading,etc. Thanks guys. Anyone out there have ANY problems with their 790? I'll post if i have any with mine. Thanks again,Charles.

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Bird Senter
Join Date: Jun 1999
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2000-11-11          21408

Charles, a hydraulic top link (or center link as you call it) is great for adjusting the tilt on implements such as blades, but it will not actually give you "down pressure" on implements, so don't be disappointed if you do that. There are very few tractors that put down pressure on the 3-point hitch. You just have the weight of the implement in most cases. ....

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Halsey Green
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2000-11-12          21420

I have a JD790 with the 70 loader and it definitely will lift the front end off the ground. If I tip the bucket with the cutting end down, it will lift the front end clear of the ground to the max of the cylinder travel. I got mine in May, have just over 100 hours it now, moved an intire hill over the summer from one side of the drive to the other to increase the turning radius. No problems, just one great tractor. ....

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Roger L.
Join Date: Jun 1999
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2000-11-12          21425

Your loader should pick the front end up easily. Doing so usually reguires that you rotate the bucket down, as the lift arm cylinders are not designed to depress much below ground level when the bucket is horizontal.
A hydraulic third point would provide down pressure if the lift arms didn't lift so freely, but they do. All you get is a change in attack angle. Down pressure was tried on small tractors 40 years ago, but I've heard that they found that any down pressure applied to the implement just lifts the back wheels by the same amount and the net result is less traction to pull the implement through the ground. A heavy tractor might be able to use some down pressure, but not our compacts. Your solution to the grading is to hang as much weight on the back blade as the tractor will handle. The biggest problem with the modern back blades is that they are no where near heavy enough. If you have such a lightweight back blade - and since your tractor has a loader - you can probably add as much as 500 pounds right over the blade. Check your spec sheet and it will tell you the lift limit on the 3pt. ....

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Charles
Join Date: Apr 2004
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2000-11-12          21434

Thanks guys. I see your point about the down pressure issue. As much as i try,i can't get the loader to pick the front wheels off the ground.In fact,as i was grading with the bucket last evening,the loader would slightly compensate for the ground condition rather than raise the front end up.The fluid level is fine,and the loader does everything else normally. Anything else i should check? Thanks again,Charles. ....

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Roger L.
Join Date: Jun 1999
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2000-11-12          21437

Charles, that does not sound right. Better look in the manual to make sure, but it sounds like you are pushing the loader valve control lever too far forward when you are trying to get down pressure with the bucket. If one pushes the lever slightly past the down pressure location then the "float" position is selected. This allows the bucket to float on the surface of the ground.
Try this: rest the bucket on a stump or a big rock or anything strong that about two feet tall. Put it in neutral and step on the brake. Now with the bucket resting on the stump, push the control lever in the direction that you think should lift the front wheels, but don't push the lever very far....just enough until you feel something begin to happen. While holding the lever in this position, gun the engine a few time. Your front wheels should smoothly into the air. ....

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Henry McCreary
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2000-11-12          21445

Hi,

I've owned my 790 with a 70 loader and 60" belly mower for about 6 months now and just love it. I will take you a little time to get used to using the loader effectively.... Remember, your not driving a D9. I can lift the front-end up with the loader only if I'm running at higher rpm's. I got worried the 1st time I tried doing it... but it was running at idle speed. The only problem I've had so far is loose battery connections. They corroded so badly that I had to replace them. ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2000-11-13          21473

Charles, what you may be experiencing is some air in the system (which is compressable, fluid is not). This is normally caused by one of two things, first (and most likely) there is still air to be purged out of the system from the attachment of the loader to the tractor's system, this can be cured by lifting the loader boom as far up as possible, then holding the control in the 'up' position for 5 seconds more, then slowly, let it back down, repeat 2 or 3 times, same with bucket control. If this is does not cure it the problem is more than likely caused by "cavitation", basically this situation results from having air trapped in the hydraulic system by too much vacuum on the return line. The cure to the problem is simple, you will need a 'one-way choke' installed in the 'down' side of the boom circuit (the side of the boom cylinders closest to the operators position). What is happening is that the weight of the loader coming down, plus the hydraulic pressure on the down side of the circuit is causing fluid to leave the boom circuit faster than vacuum can replace it on the other side, resulting in air being sucked into the lines because it is easier to 'speed up' than the fluid. The 'one-way chocke' is, just as the name suggests, a device which can choke (or reduce) the flow in one reduction, while not hindering the fluid flowing the other way, which will slow down the fluid coming out of the 'down' side of the circuit to a speed which the system can replenish the 'up' side without cavitation, but not restrict the boom's upward speed or power. If indeed "cavitation" is the culprit the first solution I described will work untill you put the loader down fast once, then it's back to 'no go'. Best of luck. ....

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Kim Hartshorn
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2000-11-14          21492

Since you mentioned that the loader was compensating for the ground, I am almost certain that you are making the same mistake almost everybody, including me :-),
makes when they first get a loader. All the way forward on the lever puts the loader in "float position" exactly so that the loader bucket will float on the ground and compensate for variation. Float takes away down and up pressure from the loader arms...so it will never pick up your tractor. Try moving the loader arm lever in the down direction...but do not take it past the detent position which is all the way forward (this is the float position) and I am certain you will pick up your front end.

BTW the stupidest thing I ever did with my tractor was the first day I had it and happened with the loader in float and in 4wd. While pulling the bucket backward with a load in it the bucket hung up on a rock, since I was in 4wd in reverse with the loader in float...the front wheels continued going backwards, the loader stayed on the ground..and I stood the tractor on its nose!

Don't do that!

Kim Hartshorn ....

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Toddh
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2000-11-14          21506

I have also had problems with the battery cable connectors becoming corroded (one was so bad it broke in half and I had to attach another one and that was after I had cleaned the corrosion off twice by hand and with WD-40). I know another person who bought a 790 at about the same time I bought mine (this spring) who has already had problems with his battery, too. I spoke to the a tractor mechanic about it and he told me that battery problems were reasonably common on 790's due to the flimsy cable connectors1. I think JD just went for cheap ends on the battery cables instead of good ones. The rest of the tractor has been great, but this in one area JD could spend $6 on and really increase customer satisfaction. ....

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DanaT
Join Date: Jun 1999
Posts: 138 Clay Center,Ks
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2000-11-14          21509

Is the battery on a 790 in front of the radiater? That is where it's at on my 855 and I have the same problem. My old 755 had the battery under the hood in front of the dash (were the fuel tank is now) it never had any problems. makes me wounder if the battery gets to much of a beating in out front of the axle? ....

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Henry McCreary
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2000-11-15          21529

I agree with Toddh, it's cheap battery cable connectors that are the root of the problem. One day she just wouldn't start and I found that my connector literaly disintegrated......... And yes, the battery sits in front of the radiator. Otherwise, it's a great tractor. ....

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