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JD 7720 Combine- Unloading (NOT)

T

THaden

Member
This is our second year with this combine. Up til now it has been flawless. The problem is when you swing the auger out to unload, the unloading system binds up and squeels the belt and or breaks the shear bolt. The first time it happened i saw the pinion nut on the 90' bevel gears for the vertical auger, was loose- i tightened it and all worked for about 2 more times. Then same thing.
Everything up to the bevel gear seems to be ok (we took chains off and checked as best we could with 200 bu of beans in it) We thought it was in the little gear box in the turret elbow. Took it out (that job sucks)but it was fine. We pulled the inspection cover off of the vertical auger housing to see if there was any thing jammed in there- no just beans coming out. Said heck with it and tried it again- it worked. For the rest of the day, when it came time to unload, just popped the cover off, let some beans out and it works.
I believe the problem is in the vertical auger and we are going to tear it apart soon, but wanted to see if any one had been there and done that or has any ideas.

Thanks
 
How do beans get in the vertical auger? Do they come in during combining or do you not unload long enough to empty the auger?
I have a 4400 and if I have a problem that requires shutting down with the clean grain auger full--the elevator to the bin--it will not start till I empty it. Answer don't shut down till the combine clears.
 
i understand what your saying because i have had my share of 4400 & 6600's. That is not the case on this. The vertical auger sits low in the corner of the tank- the beans fill the area up as the tank is being filled.
 
Is it possiable that gear box on the right side up towards the top,that has a grease zerk could be a problem not sure what they call that up their
 
check the timing on the swing auger to the vertical auger i have a7720 and no problem can stop and start any time during unload
 
not sure on the vertical, have not had it apart yet, the horizontal is good. Had to pull it out some to get to the gearbox in the turret (which the gearbox and the auger were both good)

We grease on the schedule per the schematic.

The timing i would think is good because it did work prior to this.

Thanks for ideas.
 
I"ve not seen exactly that problem, seen all the other ones. Check if the $880 sump tube for the upright auger is broken or worn out at the top and the turret elbow is moving out of position when you swing the auger out. It does help to have the horizontal bin augers covered as much as possible with the factory slides to take pressure off of the drive system and keep the rear auger from feeding the upright one too much. Make some more covers if you don"t have them on there. Usually anytime something locks up it will stretch and break the chain that drives the rear horiz. bin auger and will bend the auger just for extra fun. See if there is an older mechanic at your JD dealer that has experience with them, it will be worth what it costs, trust me.
 
Getting the upright and horizontal augers in time is very critical. It will show how they are to line up in the service manual and maybe also in the owner's manual. Some techs will time them closer together than the book says, but you really need to know what to look for.
 
The horizontal auger shields was the next thing we were going to look at. We put the machine back away due to the rain. I have not noticed any movement of the auger at the turret, it all looks good. The auger flighting edges at the gearbox are suppose to be 15 degrees apart (from my memory?). We looked at it as we put it back together EXACTLY how it came apart, it looked correct but we did not verify that measurement. Might have to now if the vertical auger doesnt appear to be the cause when we get back at it.
thanks
 
Another thought, got a bearing out/going out on the counter shaft? (runs from under the cab to over by the radiator {and then via a chain to the grain tank cross auger})
 
I worked on our 8820 unloading system way too much this year and an experienced mechanic told me he has seen beans just settle in so tightly that they will lock up the upright auger when you go to start it.
 
Do you have a chopper on your combine? Had a 7720 one time the chopper was a little out of balance, packed the beans so tight it wouldnt unload like yours, just a thought.
 
Now that you mention it...............
This is the first year we ran with the chopper on it. The combine has a slight vibration or more of a rocking sensation feeling in the cab. I know the chopper isnt vibrating excessively but it probably does compound the overall vibration. The beans packing in there could make sense, and when you open the inspection door on the vertical auger to let some beans fall out (relieve pressure) it starts to work.

We are going to take the vertical auger apart to inspect the bearings & shafts.

We are going to confirm the timing of the augers.

We are going to check the horizontal bin auger covers.

How do you balance a chopper?

I will post back to let everyone know what we find. Thanks for your help. If anyone has anything else- please share
 
Vibration could be comming from dirt in the cylinder, variable speed cylinder belt, or primary countershaft.Check your chopper knives and hardware really good, sometimes bushings will eat through the bolts. If chopper has to be balanced get ahold of local dealer, im sure they have had to send them away before. Good luck !!
 
An engine rebuilding machine shop is the only place I have heard of that will spin-balance a chopper.....and only after brand new knives and bolts have been installed.
 
Its been awhile since we had a 7720 but I remember that in the bottom of the tank where the augers are there are shields that are adjustable that will make it unload faster.I remember opening them up some and then having problems.The sump also has to be in good condition or it also wont unload right.Its probably over 20 years old so things happen.
 
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