Anyone have a JD 420? have a hydro question?

BTS

BTS

Tractorologist
Member
First I want to say sorry for all the 420 questions, I just got it going and I'm trying to sort out a few issues.

Anyway, the hydro on it seems a little odd to me, but maybe that's the way it's suppose to be. When I take off on it (lets just say I'm running it in high), the engine is at full throttle and I move the hydro lever all the way as fast as it will go. The 420 will take off at a medium speed and slowly speeds up till it's running full out. I have the same issues in low, even when I was running the 3-pt blade, I would be running it slow (at full throttle) and as soon as the blade touches the ground it will stop the 420. I would then have to move the hydro lever forward to have enough power to pull the blade but as soon as the blade lifts up the 420 takes off fast due to there being mo more resistance from the blade.

Could this be caused by having the wrong oil in the hydro? I'm not overly sure what's in there but I know it's suppose to run Hy-Gard. Or is this how these hydro's are?
 

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That seems odd to me. But I have no experience with JD and don't even know what hydro they used.
 
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That's not how it should be at all! But not being familiar with the 420, I don't truly know what to tell you. Is your lift function strong? It kinda sounds like the hydro is simply worn and pressure escaping at the valve plates.
 
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I would check your relief valves on the hydro, then check the fluid. There should be a site glass on the right side of the rear, you should see fluid at least half way up the glass portion.
 
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It is full on fluid, where is the relief valve at?.
The lift seems really strong, the 3-pt can pick me up at a idle and that's more weight then I'd like to post :oops::cool:.
The garden tractor has just under 1000 hours so I wouldn't hardly think it would be worn out, but it is John Deere after all :p:)
 
If the lift works good then I would start looking at the hydro control linkage, they are known to get sloppy over time. The hydro relief valves are under the seat pan, they are located at the top front of the hydro pump. There is button on each one that should be sticking out with the tractor and pump running. It is the same pump used on the later 140's, 300-318 series.
 
Man I just had the seat pan off a couple weeks ago when I had to clean out the fuel tank lol.
I will look into the relief valve, while I'm at it I will go ahead and replace the filter and oil. I will also look over the control linkage.
Thanks for the help!
 
JD has a pretty decent price on the fluid, at least down here. About $14 a gallon. Just did the 316, it had red fluid in it. But it was milky.
 
The local hardware store here sells it and it is quite expensive, I don't remember the exact price but it's about double the cost of the cheaper oil. I wonder on if it's really any different then any other oil??? seems like everything with John Deere stamped on it is twice the price.
 
I got the recommended Low-Viscosity and it's pretty thin, kinda like type-f fluid only clear. The 316 seems happy with it. Wonder how an Eaton would do with this? The 420 should be a Sundstrand 15, I think. That's what is in the 316.
 
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