John Deere 7720 maintenance - The Combine Forum
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post #1 of 14 (permalink) Old 02-03-2016, 01:05 PM Thread Starter
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John Deere 7720 maintenance

Hi, this is my first year owning a combine, I'm just getting started in custom work. Besides changing the oil, what other oils are there to change. I'd like to change the hydrostatic oil and hydraulic oil, how often should that be done. I also would like to know of any other spots where gear oil may be used. I think there is one by the dual cylinder drive and the gear reverser for header as well. I know I may be missing some, Is there one by the loading auger? Thanks for the help

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post #2 of 14 (permalink) Old 02-03-2016, 07:28 PM
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Unless you have the service records of the combine it probably would be worth the time and money to change all the oils.
The Hyd filter is in the tank and so is the hydro.
The hopper fill auger gear box is grease not oil, the unload auger has a greaseable bearing at the bottom and at the top there is a grease nipple at the elbow.
There is a grease nipple for the main power shaft off the motor under the cab. Its not one you can see but if you put your hand in there you will feel it. This is one area that gets missed a lot of the time.
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Last edited by V876; 02-03-2016 at 07:38 PM.
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post #3 of 14 (permalink) Old 02-03-2016, 08:05 PM
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when I got my 8820 I changed the reverser oil, final drives, transmission, hydro, hydraulic, two speed cylinder. in the hydraulic and hydrostatic tanks there is a filter.

got a new copy of the owners manual and made sure I could find all the grease zerks and they all worked.

start at the front and just take piece by piece. feeder house check the floor tins, chain tension, find the S clips on the feeder house chain and make sure there still good, top shaft sprockets and bearings. cylinder and concave, belts... just work your way back. gear box on the grain tank fill auger, I would put a half tube of grease in him, same with gear box on unload auger elbow.

get a winter inspection form from the local dealer and use it.
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post #4 of 14 (permalink) Old 02-03-2016, 08:54 PM Thread Starter
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Thanks guys not around combine now, but where are hydro and hydraulic tanks, I know one of them is on left side of combine about in the middle.
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post #5 of 14 (permalink) Old 02-03-2016, 09:04 PM
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Thanks guys not around combine now, but where are hydro and hydraulic tanks, I know one of them is on left side of combine about in the middle.
That would be the hydro.
Hydraulic is beside the cab in front of the engine.
Many of these questions will be answered for you if you read the owners manual.

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post #6 of 14 (permalink) Old 02-03-2016, 10:45 PM
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One grease fitting that never made it into the service section of the manual is located behind the lower cylinder variable speed pulley. It finally was included in the 50 series combines. It is a bit of a bugger to find but it really saves drive belts when your posi-torque drive is working properly.

Sheet 5.jpg

The other part of the manual that is really important is to properly follow the grease filling procedure for the lower variable speed pulley. The variable speed belt can be a **** to change at the best of times, and burning up belts due to a poorly maintained variable is frustrating. Keep it greased properly and it will not be a problem.

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post #7 of 14 (permalink) Old 02-04-2016, 08:03 AM
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where are hydro and hydraulic tanks,


On a 6620, the hydraulic tank is under the door on the side of the combine right behind the entry door into the cab. The hydrostat tank is on the same side of the machine towards the rear and up. The hydrostat takes low viscosity hyd oil.
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post #8 of 14 (permalink) Old 02-04-2016, 01:10 PM Thread Starter
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Thank you I will have to look into smaller cylinder pulley and how to maintenance lower variable pulley. May not be doing it how the manual calls for? Another question that is a little off topic is about my custom cutting, I have a guy that wants me to cut 236 acres of beans for him. I have a clear schedule next fall and can cut when ready, but am skeptical of capacity of machine and timeliness. I have a 925f header for it.
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post #9 of 14 (permalink) Old 02-05-2016, 07:07 AM
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You should be OK with the 925 head. It will be a load on the combine, and you aren't going to set any speed records, but you should be OK as long as the concave and bars are in good shape.. I used to run a 220 on a 6620 in 50bu. beans and got along about 3.5-4mph.
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post #10 of 14 (permalink) Old 02-05-2016, 12:06 PM Thread Starter
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Okay thanks guys, as far as a backup plan I'm trying to figure out in case of a breakdown, is it plausible that my backup could be a rental from a dealership. Are most dealers willing to rent out a combine hourly or not so much? Any other suggestions

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