800 Lift cover rebuild questions.....

mrf1002u

Member
Hello,

So, my 800 had a drifting down issue with the 3 pt.

Pics:
https://www.dropbox.com/sh/6zku5c10svw3c7h/AAAd3cyhdqfW6j5-ow2K3q2ya?dl=0

I have the top cover off and parts ordered. During teardown, I found a piece of what looks like red RTV in the area between the Unloader Valve (C9NN925A ) and the Unloader Valve Bushing (957E482A), 11 and 13 in the parts diagram. I want to make sure I have any remaining chunks cleaned out.

The service manual shows a tool to remove and install the "front and rear unloader valve bushings". How is it done without the tool? And do they actually need removed??? At first I thought there was an o-ring between the two parts, since the New Holland diagram shows it twice, but I guess the lower o-ring #7 is the same one shown up higher in the New Holland diagram for the unloader valve. The parts manual reprint only shows it once. Confusing at first.

So do I just flush well and leave it as I have it in the pictures in my link. Or, do I try to remove these other parts?

Also, is the o-ring (NCA836B) a direct replacement for the split steel ring (C9NNH893A) on my unloader valve now? Just remove the ring and substitute the o-ring?

Is this o-ring (NCA836B) in the top cover gasket and seal kit I ordered from this site?

Sorry for all the questions, appreciate the help.
Thanks,
Larry W.
 
This is why one should NEVER under any circumstances use goop in place of the proper gaskets and O-rings on such machines. I've found goop in the hydraulic pump valves as well as other places when some "mechanic" in the past was too lazy or in too much of a hurry to buy (maybe order before buying) the proper gasket(s), O-rings, etc.

In a hurry so did not reference your photos, etc., but can say equivocally, that you will save yourself time and trouble if you buy a genuine CNH unloader valve O ring (insist that it is in a genuine CNH package, as dealers often sell aftermarket parts as CNH, sometimes in CNH packaging) rather than an O ring from an aftermarket kit.

You will likely end up kicking yourself if you do not.

Dean
 
"Also, is the o-ring (NCA836B) a direct replacement for the split steel ring (C9NNH893A) on my unloader valve now? Just remove the ring and substitute the o-ring? " Reasonably sure that the valve (spools) are different for iron ring vs O-ring.....so, I expect 'no' on the direct replacement question. You can try the rubber O-ring on it & if not compatible, as I expect. you will likely find it obvious in the fit.
 
(quoted from post at 19:12:47 07/15/18) This is why one should NEVER under any circumstances use goop in place of the proper gaskets and O-rings on such machines. I've found goop in the hydraulic pump valves as well as other places when some "mechanic" in the past was too lazy or in too much of a hurry to buy (maybe order before buying) the proper gasket(s), O-rings, etc.

In a hurry so did not reference your photos, etc., but can say equivocally, that you will save yourself time and trouble if you buy a genuine CNH unloader valve O ring (insist that it is in a genuine CNH package, as dealers often sell aftermarket parts as CNH, sometimes in CNH packaging) rather than an O ring from an aftermarket kit.

You will likely end up kicking yourself if you do not.

Dean

Thanks Dean,

I will take that advice, partly because if it isn't labeled in the YT kit, I might not get the right one anyway. LOL

I did order the lift piston o-ring and backer form Messick's, after reading previous posts about not using the ones in the YT kit. Haven't gotten them yet, but looked to be CNH parts on their site. I need to get the dowel pin that rides the cam anyway, so I'll order that o-ring from Messick's at the same time. I do not have a dealer anywhere close.

Someone beat me to the idea of removing the pin and putting it in the other way. It had TWO worn spots on the opposite end already. LOL

Larry W.
 


Thanks JMOR,

After some more digging, it appears that you are right, but apparently the unloader valve C5NN925A for an o-ring, was replaced by valve C9NN925A which uses the split ring. It also appears theeven newer number is C9NNH893A.

The split ring is the newer part. Maybe after 1953. That is from Messick's parts list.

Given that I found red RTV in the unloader valve area and the fact that the new split ring is $46.00, I may reuse what is there and install the rest of the new parts and see what I get. If I have to tear it down again, then so be it.

Here is the valve and ring in mine. What do others think?
https://www.dropbox.com/s/2vjk5fo7qgw1jbo/IMG_2078.JPG?dl=0


Larry W.
 
So...

Look at T3 here.
https://www.dropbox.com/s/nnfr461dela4bye/Unloader%20Seal.jpg?dl=0


Mine was apparently serviced at some point with newer parts from the 70's. Given that I have a chance of breaking a $46 ring trying to get it on the valve, I will try what I have and fix all the other stuff I found wrong first. If I have to tear it down again.........then so be it.

Thanks all,
Larry W.
 
BTW.

I used this, that I already owned, to remove my cam follower pin.

Ball joint service kit. Just the big C clamp and screw part.

Its a bit tight to get it just in the right place, but it came out so easily!

https://www.harborfreight.com/ball-joint-service-kit-for-2wd-and-4wd-vehicles-63279.html

Larry W.[/img]
 
(quoted from post at 15:28:22 07/15/18) Hello,

So, my 800 had a drifting down issue with the 3 pt.

Pics:
https://www.dropbox.com/sh/6zku5c10svw3c7h/AAAd3cyhdqfW6j5-ow2K3q2ya?dl=0

I have the top cover off and parts ordered. During teardown, I found a piece of what looks like red RTV in the area between the Unloader Valve (C9NN925A ) and the Unloader Valve Bushing (957E482A), 11 and 13 in the parts diagram. I want to make sure I have any remaining chunks cleaned out.

The service manual shows a tool to remove and install the "front and rear unloader valve bushings". How is it done without the tool? And do they actually need removed??? At first I thought there was an o-ring between the two parts, since the New Holland diagram shows it twice, but I guess the lower o-ring #7 is the same one shown up higher in the New Holland diagram for the unloader valve. The parts manual reprint only shows it once. Confusing at first.

So do I just flush well and leave it as I have it in the pictures in my link. Or, do I try to remove these other parts?

Also, is the o-ring (NCA836B) a direct replacement for the split steel ring (C9NNH893A) on my unloader valve now? Just remove the ring and substitute the o-ring?

Is this o-ring (NCA836B) in the top cover gasket and seal kit I ordered from this site?

Sorry for all the questions, appreciate the help.
Thanks,
Larry W.


Well, I got the check valve seat and the check valve out of the lift cover, but, MAN did that thing come out hard. I can see where they would get broken. Never had a tractor with hydros before, but the end that faces the check valve and the check valve itself both have a black spot where they meet that I have read indicates a leak. I bit the bullet and ordered both parts new from Messick's. Ouch!. Have not read in the manual how to put it back in, but I hope it goes in easier than it came out. Any hints are appreciated.

Also ordered a 25 pack of 15/32" balls on Amazon.

Larry W.
 

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