JD 2120 hydraulics

[nokiddin]

Hey all. I have a jd 2120 (the old one) that has 2 sets of remotes at the back of the tractor. 1 set runs the after market 3 pt, and works great. The other set will only push a cylinder one way.

I did ensure the cylinder works fine on the other remote.

I changed the QCs, which did not fix.

From what I understand, the poppet valves or spool valves could be stuck.

Is there any way to test this? Or do I just have to take them apart and inspect.

Lastly can this be changed on the tractor or does the scv need to come off? I wouldn't mind a little guidance in the procedure if someone could help me out.

I would really like to get it working so I can control the chute on my snowblower!

Thanks in advance!

 

[Tx Jim]

Can you please post any photos of your tractors scv's? Poppet type control valve would require removal from tractor to adjust the valves. There are 2 different style scv's listed in 2120 parts catalog. One can check pressure by installing a 3000-5000 psi gauge on a male breakaway tip then plug in and operate scv control lever. I would also be interested in viewing photos of your tractors aftermarket 3 pt hitch because I was unaware an aftermarket 3 pt for that era JD utility tractor was available.

 

[nokiddin]

Here are some photos Jim. Hopefully you can make it out, I know there is a fair amount of grease and oil on them.

I did notice that when I push the lever forward, I can easily feel a click as the a internal component on the lever pin hits its limit on the top/back of the housing. I can feel something similar on the working side, but it's much less distinct or noticeable.

The 3pt has a Groening label on it, but it may have been modified to fit this tractor. It was already on the tractor when I bought it.

Thanks again. View attachment 683420

 

[Tx Jim]

Your photos are the 1st I've seen of a JD 10-55 series utility tractor with aftermarket 3 pt hitch. The trans cover on your tractor must have originated on an industrial model designed for a backhoe. Your tractor's scv contains the 4 poppet valves. These valves to be adjusted correctly require to have the rockers loosened. The clearances are not very easy to correctly adjust. The click you feel is a roller entering/leaving detent notches in the rocker plates.

 

[Zebrafive]

If you have not tried to adjust the four set screws that have locking nuts, you may not have to do any adjustments. Just check the four poppets, two pressure and two return. Marked in red in drawing with a 4
There is also a detent which it sounds is OK
A Metering valve, marked M, and a Flow Control valve marked FC
You have to remove the SCV and take the bottom cover off. The poppets are spring loaded, watch out you do not lose parts.
First drawing is the adjusters set screws and lock nuts
Next drawing is detent for the lever
Last drawing is Poppets (4), Metering valve (M), and Flow Control valve (FC) The seats for valves in the housing are not replaceable. There is repair kit, NJD150, see a dealer if the seats are bad.
Check the poppets for scoring, also their bores in the housing. Check the rollers for pitting/flat spots. Replace all O-rings, Packings, backup rings.

 

[nokiddin]

Thanks for all in the info!

Today I hooked up a cylinder to it, and found that if I pushed the lever forward, the cylinder moved out, if I pulled it back, nothing happened.

Then I switched the lines around, and if I pushed forward, the cylinder came back in, but if I pulled the lever back, nothing happened.

I was wondering if this helps point toward any particular valve, or other component?

@TxJim, I didn't realize my tractor was such a Trendsetter with its 3pt! Interesting how you noted that the trans cover is from an industrial model, since I have noted yellow paint in places where the green has worn off. I knew the tractor was painted to make everything JD green, even the Allied (I think) loader.

Was there a 2120 industrial model?

 

[Tx Jim]

No there was no industrial 2120 to my knowledge but most parts will interchange between JD AG & ind 20-55 series models. Industrial models were built in Dubuque,Ia & 2120 was built in countries other than USA. My guess is previous owner of 2120 had difficulty with original rockshaft housing(probably cracked) & installed trans cover with no rockshaft

 

[Tx Jim]

Zebrafive
I agree one might sneak by without the need to adjust the poppet valves BUT my guess is that ""ain't happening"".

IMHO JD engineers made that SCV valve way to complicated to perform the simple task of controlling hyd cylinder. A simple spool valve set up for closed center operation will accomplish the same task with fewer parts. Granted when spool &/or housing receive sufficient wear both parts must be scrapped in lieu of repair for JD SCV but compare the repair/replacement costs.

 

[Zebrafive]

Zebrafive
I agree one might sneak by without the need to adjust the poppet valves BUT my guess is that ""ain't happening"".

IMHO JD engineers made that SCV valve way to complicated to perform the simple task of controlling hyd cylinder. A simple spool valve set up for closed center operation will accomplish the same task with fewer parts. Granted when spool &/or housing receive sufficient wear both parts must be scrapped in lieu of repair for JD SCV but compare the repair/replacement costs.

I think this (poppet valve era) was when JD engineers "over engineered" a lot of things. Now it's all about having electronics control everything. :thumbdown:

 

[Tx Jim]

I'm very happy that my 3 tractors aren't electronically controlled & even happier they don't have common-rail fuel systems.