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need help with broke JD 494 corn planter


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 Has anyone out there worked on a John Deere 494 corn planter? The 20 years I have had mine I never gave a thought as to how it worked, just kept it greased and it planted my corn & soybeans every year. I got half way done planting beans this week & something broke & it stopped planting. & not understanding how it functions I'm at a loss. I know when lowered it engages the drive sprocket on the right side of the gear box & turns the square shaft that turns the seed feeders & when raised it disengages the lower drive sprocket. I took off the chain & the lower drive sprocket turns freely in both up & down position not turning the square shaft. I'm thinking in the down planting position something in the gear box should be engaging this sprocket so it does not free wheel on the shaft & that is what broke. Also I can not understand how the drive chains on the wheel hubs engage the gear box when the planter is lowered to the planting position. Don't know if these photos will help explain what I'm talking about, thanks for any knowledge you have from your personal experience with this issue.

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I never worked on one, but figured it shouldn't be too hard to figure out. I never really looked at one of these old Deere planters, but looking at your pictures, had to say wow that's heavy duty.

I can't see the left side of the gearbox well in your pictures but there's got to be some sort of linkage there that is actuated by lifting/lowering. That runs a clutch inside the center gearbox. If the external linkage is ok, something is wrong inside that case. 

https://partscatalog.deere.com/jdrc/sidebyside/equipment/74962/referrer/navigation/pgId/24257

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I had a similar model many years ago. I think , I repeat think that there are cams that engage when lowered to plant and I had to weld them to fit with both halves. Not really sure if this could be your problem. Good luck 

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Is there a pin sheared off somewhere? I’ve been running a 494A for way more years than I ever thought I would… but I’m having trouble picturing what your issue is. 
Is the drive wheels turning the input shaft freely?

Is the transmission engaging ? I’m thinking it’s just a simple issue like maybe packed full of 20 year old dried up grease and it isn’t allowing the pieces of the clutch to slide together to engage… but it’s been a few years since I’ve used mine… 

If I’m remembering correctly that clutch is simply an over running clutch and when you lift it the lifting rod separates the 2 halves. When you put the planter back down it releases the half and spring pressure(?) pushes them back together 

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When I was a little kid I rode on the back of the belly mount version. There was a seat back there to sit on while I  watched the chains. They were all driven by the press wheels. I was the planter monitor!

I will guess there is a disconnecting sprocket that is opened by linkage when you lift the planter. Similar to a grain drill. However that is a wild guess.

Thx-Ace 

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