Go BottomJD850-4WD Clutch upgrade
 | Jim Pearson
Join Date: Jul 2003 Posts: 3 TX 
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2002-03-30 36890
I have a 1986 model John Deere 850 4WD compact tractor in need of clutch replacement. This model is equipped with a two stage dry clutch with two friction discs. The PTO still engages and works fine but the drive disc slips bad and will not propel the tractor except in low range at very slow speed. I have located a complete replacement clutch including pressure plate and both discs from an aftermarket supplier of O.E.M. parts for around $650.00. Before replacing this clutch with an O.E.M. equivalent, I would like to know if I could upgrade to a bigger or stronger clutch for this model. The original factory clutch just dosen't seem big enough to handle the loads of this 4WD tractor. My repair manual shows the same clutch configuration for the Model 950 as my Model 850. I don,t think the Model 950 clutch is any bigger than my O.E.M. clutch. I would like to know if I could adapt a bigger clutch to my tractor, even if it requires some modification. If anyone has any experience with this, please let me know.
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada 
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2002-03-31 36900
My friend at the local Deere dealer tells me that the clutch on this model burns up because folks try to do heavy work like pulling a box blade full of dirt in a gear that is too high. I guess that is one way of saying that the engine is stronger than the clutch. His advise would be to work slower and at higher rpm's when you get that new clutch installed and it should have a normal life span. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-31 36905
It seems like curious engineering if the combination of engine torque and tire traction is capable of overcoming clutch disk friction. However, such a design would provide protection for drive train components against load shocks. It might be cheaper to replace a clutch occasionally than to fix broken TX's etc.
It's good to keep in mind that things are usually engineered in a system when considering something like a heavy-duty clutch. Stronger springs in the pressure plate might solve a slippage problem but also might break something. A larger diameter clutch also would do it but usually would require a different flywheel bell-housing etc. and also might break something.
I know the clutch has to be fixed now and that's an aggravation. There's may be no such thing as a heavy-duty clutch that's consistent with the overall engineering. After the fact prevention advise isn't very satisfying, but slower ground speeds and lower gears help. Above all, clutches should not be feathered especially when under heavy loads. Feathering clutches is a good way to create large repair bills.
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| Jim Pearson
Join Date: Jul 2003 Posts: 3 TX
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2002-04-18 37614
Is there a website that you can download data from factory repair manuals for a JD 850 tractor? What are other sources to purchase repair manuals other than I & T manuals? I have an I & T manual but it does not show very much detail in some areas. Does anyone publish any good aftermarket repair manuals like Clymer or Chilton does for cars and trucks? ....
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| BillBass
Join Date: Feb 2002 Posts: 190 North Texas
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2002-04-19 37622
I have a 1984 JD 950 with 2100 hours. The clutch does not slip at all. Under load, either the tires break loose or the engine lugs down, but the clutch never slips.
If you bought the tractor used, it may be that the previous owner had a habit of keeping his foot on the clutch pedal and slipping the clutch when working.
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