Late 4020 SCV

[jonesrj]

We are looking to add a 2nd SCV to a 4230. We've had a valve for a long time off a late model 4020 a guy had junked, if memory serves. I'm familiar with the 4230 SCVs and I thought the one from the 4020 was the same until we got it out of storage and saw two casting lugs on top and few other obvious differences. The detent piston was stuck and after opening it seems like we've got a oddball.

The first picture from the parts book shows the two cast cylinder lugs on top, but they're shown to be plugged. Ours has no plugs and never did, just blank casting. Also that picture shows the detent bore to be separate from the valve cover. Ours is not like this, but has the regular cover similar to the 4230s. The valve does have the detent cam cast into the rocker like what I circled in the picture. I had never been into one with no detent spring, but the 2nd image shows the detent piston and pin like what is inside the valve.

It appears as if JD was in the process of changing design/tooling when this valve was made. I'm sure there are other valves like this still in good service today, but would I be better off trying to find a later valve to put on? If I do proceed with building this valve to put on 4230, is there some things I should definitely do to update this scv? The odd springless detent is a bit of a curveball. Thanks.

 

[Tx Jim]

If 4230 was under my supervision I would bolt scv to rockshaft housing, insert breakaway male tip with gauge attached alternately in each breakaway coupler, with engine operating at idle pressurize both sides of coupler & if pressures were within spec's call it good. If pressures weren't with spec's then I'd attempt to determine the problem which would most likely be faulty valve seats or incorrect valve settings. Newer scv utilized hyd vs spring pressure to hold control mechanism in detent position. This update happened on 4230 @ serial # 040165.

My guess is scv ports with plugs you referred to was used in very limited applications because I don't remember seeing that style in person.

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[jonesrj]

Thanks for reply, yes we originally tried doing as you suggested (mounted to tractor and tried to operate valve) but the detent piston was stuck in the bore and lever wouldn't move. We took it back off and opened it to get the detent freed.

I see the break at sn 040165 but all the detent parts seem to be the same on both sides of that for 4230 scv, including the spring. So I'm confused on what you mean with hyd vs spring pressure.

For the late 4020 scv, the original detent parts are NLA but JD offers a replacement kit that looks more like the ones I'm used to seeing. I don't know how to set the valve without detent spring so my first thought was to get the replacement detent. But I dont want to throw money at parts if if this style scv is going to end up giving more headaches later.

 

[Tx Jim]

Sorry for my posting incorrect information. I should have checked part #s more closely. I just noticed serial break & my mind assumed detent parts appeared different.

 

[jonesrj]

Sorry for my posting incorrect information. I should have checked part #s more closely. I just noticed serial break & my mind assumed detent parts appeared different.

No worries, I appreciate your effort.