1978 John Deere 850 Project

[wct097]

So the milky "overfull" fluid looks normal, clean, and at the proper level now. I think that indicates air/foam in the fluid when running. Going to check the o-rings where the hard lines meet the pump, swap the filter, and check the connections. If that doesn't improve things, I'll be looking to replace the pump.

I think I have the 9cc pump. Will try to upgrade to the 11cc model since I have a loader and power steering.

 

[Thaduck]

My Dad gave me his old JD 850. Been sitting a little while. Would you mind sending me the tech manual? It Run hot, then I realized There is steady bubbles in coolant tank even when just starting up. Along with black water sprinkles put exhaust. Hopefully just a leaking head gasket.

 

[beenthere]

Would you mind sending me the tech manual?

Thaduck: :welcome: to TBN

To whom are you addressing that question about the tech manual??

 

[thepumpguysc]

I would imagine, anybody that has 1..

 

[Thaduck]

Thank you! I clicked reply on 1 of the first few post of this thread. Should have clicked “reply with quote”. But yes I would love to have a pdf of JD 850 tech/service manual from anyone.

 

[wsguerin]

I know this is an ancient thread but what jd110 described, about the rusted snap rings, is exactly how my 850 SCV valve failed. about ten years ago, I managed to fix the one piston (controls the bucket) but sheez, what a dumb design that a $.05 part causes such a drastic failure. I tried to fix it again last year but the snap ring was more like a wire that the "C" clip I used last time and the cap passed right by it. It's a huge pain to take it off the tractor, a real head banging knuckle scraper. Any tips on fixing the snap ring?

 

[RDJD850]

Is anybody still following this thread? I'm a brand new 850 owner and new to this forum. I'm having the same issues with the SCV. I've been looking everywhere for an AR88090 or an Eaton 30922-DSC. Haven't found anything yet. Waiting on a call back from All States about finding one from a dismantled tractor, but I don't know what condition it would be in. Any suggestions on where to find one. I'm also thinking on buying the interior parts and trying to rebuild it. I've found all of the parts except for a "Cap" AM38628 and washers M46768. Any suggestions on where to look? Under a load, hydraulic oil is leaking out of the top of the two cylinders, which don't have plugs. Under a heavy load, the oil will squirt out. Any suggestions on how to repair this instead of complete replacement of the SCV? I am definitely not a mechanic, but I'm fairly handy.

 

[beenthere]

RD
:welcome: to TBN
Let's hope you can get some help for the problems, and TBN usually can come through.
If you can, get some pics (we like pics) pointing out the problem(s) and focus members attention on the location and parts you mention. Hang in there..

Pics pointing to the problem wsguerin mentions may draw some help too.. The "wire" mentioned might be the part in the hyd. cylinder, but don't know that for sure.
Sometimes descriptions don't help much without a good pic or two.

 

[RDJD850]

Thanks beenthere. I’ve got a few pics but can’t figure out how to post them from the app. Help?

 

[RDJD850]

Here are 3 pics. The first is the top of the SCV showing the two open middle cylinders without a plug in the top. The parts diagram shows plugs should be in the top of both. The second pic is a close up of the 2 cylinders showing a hex opening. A hex wrench can be used to tighten or loosen them. The 3rd pic is showing the two loader control levers that are attached to the SCV. You can see that the far right lever extends well beyond where it should stop. I think it blew out about 2 gallons of oil/fluid when I pulled that lever back too far and it stuck in that position. Is the SCV repairable or do I have to find a new one from a salvage yard? The SCV unit is obsolete and I can't find it anywhere, but I haven't called salvage yards yet. I can find all of the internal parts (o-rings, clips, plugs, bushings, etc), but the left side cap is obsolete and the actual pistons are part of the SCV unit (AR88090). Any help or advice would be appreciated!

View attachment 666846View attachment 666847View attachment 666848

 

[beenthere]

Thanks for the pics.. when you called those "spools" in one post "cylinders" and then "pistons", had me confused. Those spools are fitted to the body of control valve and why they only come as a unit and not stocked as separate parts.

Hope someone smarter than I can chime in... and help. Salvage yards may be the best place to explore. Or a machine shop that might be able to fabricate some parts like that cap key #2

 

[RDJD850]

Thanks for the pics.. when you called those "spools" in one post "cylinders" and then "pistons", had me confused. Those spools are fitted to the body of control valve and why they only come as a unit and not stocked as separate parts.

Hope someone smarter than I can chime in... and help. Salvage yards may be the best place to explore. Or a machine shop that might be able to fabricate some parts like that cap key #2

Thanks beenthere. I've got all of the parts I can find ordered. Is it possible to pull the spools out of the SCV and replace the o-rings, springs etc? If so, is it a job an amateur can tackle successfully?

 

[beenthere]

RDJD850

possible to pull the spools..

I'd encourage you to give it a try.. best way to find out and learn.

Have you looked hard for the Eaton 30922-DSC that you mentioned in your first post in this thread? That one was mentioned earlier by the OP as being a direct replacement and worked well for him.

Here is one listed at MobileValve.
Eaton 3922-DSC Mobile Valve

Maybe others, but you may have exhausted all those possibilities.

Good luck..