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replaced RH bearing and collar on primary countershaft because collar had broken away approx 300 separator hours ago. Just finished harvest and noticed collar broken away again! Anybody have any idea on what would cause this? Not happy, big job!!
 

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You should pull the shaft out and check the left side splines for wear. They engage in the primary countershaft gearcase and will cause vibration when worn. The other problem with these shafts is the welds letting go where the shafts are joined together. These shafts are made of 3 pieces- left and right solid machined with a hollow tube in the middle. You can see the right side weld through the oval hole in the frame just to the inside of the bearing you replaced, looking from the bottom. I have also seen them go out of true. When you have the shaft out put it in some v-blocks and check it for runout with a dial indicator. Should be .005" or less. Most good machine shops can straighten them. I think a new shaft is roughly $3k
 

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It is either worn, or corkscrewed, or both. Similar problems with 7700, 7701, 7721, 8820, and so on up the line. Worst one I pulled out of a 7721. New bearing were 0.015 bigger than the shaft it was that far gone. We took out the shaft and put on V blocks to find out how bent it was. If you measured the high spot in the shaft about every 6 inches along the shaft, the high points would make a curved line along and around the shaft and looked like a cork screw. Pulleys on either end would have a slight vibration to them all the time. New shaft, bearings, and bearing holders solved all the problems.

9500, 9600, and up bend the same way, and are a bit harder to change. Sorry to say, but if you choose to repair, don't scrimp on the repairs, or you will be doing the same repair again very soon. It is pricy, but if you plan on keeping the machine for a few more years, rebuild it and you will have the peace of mind that it will stand up and work the way it should.
 

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I remember helping change out the shaft in our 8820 years ago. (Twice actually!) That was a job!

When/why did Deere go to a 3 piece shaft/tube design? The 8820 was a solid shaft. Still have about 3/4 of one left on the scrap pile.

Andrew
 

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When/why did Deere go to a 3 piece shaft/tube design? The 8820 was a solid shaft. Still have about 3/4 of one left on the scrap pile.

Andrew
They started that design with the 9000 series in '89. I would say that the tube style would be stronger and not go out of true as easy with a larger diameter. No doubt Deere was gearing up for more horsepower/torque with the 10/50 series and needed a better design seeing that 20 series needed those bearings done every 1500 hours.
 

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I always thought bearing locking collars are tightened in the opposite direction of shaft rotation.
Nope, that's the direction you turn them to release them. Though more than once I've seen them done backwards, so you are not alone;) Some operators manuals, like the older New Holland ones always had a very good pictures showing such, tried to find something online but couldn't.

The reason you turn them the same direction as rotation to lock them, is the collar is locked by the set screw to the shaft, that is the purpose of the screw, and then if there is any movement of the inner bearing race on the shaft, the collar will actually tighten even more. If you lock them backwards, any movement and the collar has become totally ineffective.
 

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Thanks of explaining that Albertabuck. I'd heard that they should be tightened in the direction of shaft rotation (not knowing why), but have always tightened them opposite to the rotation, in the belief that if anything struck the locking collar while running, it would tighten. Hadn't considered the inner bearing rotating.

Can't remember any coming off, so perhaps it doesn't make much difference?
 

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I had some fun some years back with the primary countershaft in my 9500.

Smelled smoke late one day when combining, and found we had a smoldering
fire in the plastic tube where the shaft goes behind the cab. Chaff loads in there
and no good way to keep it clean. Lots of air hose work and the water hose to put that one out. Later, we found shaft damage from the heat, and so we replaced
the shaft. Had to cut a hole in the grain tank to get to the fire problem.
I do remember our farm ins. helped with the cost.

The question was brought up about an open flame.
 
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