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Discussion Starter #1 (Edited)
Hi All,

So, I recently picked up a second 400 (this one is a 1982 model, with the original Kohler K532 and 809 hours and the hour meter looks original and still works). Seems that it runs real good and I'll run it as long as it will run. I had to repower my first 400, but it had a lot of hours on it and I wasn't going to spend the money for a third valve job, but that is another story for a different day.

Here she is loaded and getting ready to come home:

400#2.jpg

On the new 400, when you move forward/backward, it does not start moving until you are about 3/4 of the way to max and even when put to max speed, it does not go full speed. It acts the same in both low and high gear on the transaxle. Now, here is where it gets a little interesting. If you bump the middle hydro lever a few times, it will get to full speed. You have to get somewhere between lifting and setting the lever in float mode. Once up to speed, it will stay there. If you pull the speed back and go forward again, you have to repeat the bumping process.

The hydro fluid and filter have been changed, and it is full.

Other things of note: the tractor does have the 3-point rockshaft, but no lower arms. (I think this is likely because one of the ears is broken off.) That likely has nothing to do with the problem. Second, i see that this tractor has a second smaller hydraulic cylinder under the front end that is connected to the steering linkage. I think this was added to give the unit true power steering, rather than just power assist, as the original steering cylinder is in the original spot under the fender pan. It also steers easier than my original 400, which does not have the second cylinder.

My thought is maybe there is a check valve that is not working properly and/or sticking open/closed. Has anyone else in the forum experienced this issue and if so, any thoughts on how to fix it?

Thanks in advance for any thoughts/suggestions.

JDS
 

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It almost sounds like the scv is hanging up in the forward detent. I've experienced some weirdness in the drive with the valve in float. Mine shows up as the loader (empty bucket) wanting to raise up when starting to drive if the valve is in float position. Just a hunch. BTW, I'm pretty sure the axle housings are right and left specific. Jay
 

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Jason,
A fellow can never have too many JD 400's. Indeed, a problem with the by-pass/relief valve in the implement control valve assembly could explain part of the odd response. Check out this thread and the earlier thread referenced there: http://www.wfmachines.com/forums/sh...trol-valve-question?highlight=400+check+valve. Hydro linkage isssues could also contribute, particularly a worn spring pin in the flat control arm on the side of the tranny.


Your mention of the two steering hydraulic cylinders is puzzling. The standard configuration has a steering control valve on the drag link under the left foot rest, and the hydraulic steering cylinder is alongside the front axle. Is the set-up actually different on your newly acquired tractor as compared with your first tractor? If so, some pictures would help.
Harold
 
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Discussion Starter #4
OK, went to the other property today and looked at my original 400. Turns out, there is a second cylinder under the front end on that one too. I don't know why I did not remember that one, but I can likely knock that out as a potential difference.

jdalchemist, not that I really want to show my ignorance, and I love me some acronyms, but what does "scv" mean?

I will have to check on the other thread and read through it all in detail. Seems like that could be the answer that I am looking for. Thanks again to everyone who responded so far....

JDS
 

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Jason,
I actually did not use the "scv" acronym, but it means the implement control valve assembly.
Harold
 

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Discussion Starter #6
Thanks Harold...you are correct. GrandpaJay used the term. In any event, thank you for explaining that to me.
 

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Discussion Starter #8
Now I see that you two were the experts rendering advice in the linked post. Unfortunately, the other post links to another post, which unfortunately goes to a dead link. Is this something related to the site conversion? Think we can get Terry Reed to fix for us???

JDS
 

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Discussion Starter #9
This is starting to sound like the bypass valve is in fact defective. I notice on the new to me 400 that the power steering is much smoother, like more traditional power steering (versus just a power assist). That is what led me to believe that there was not a second hydraulic cylinder on my original 400, when it was there all along. If the valve is stuck open, then it may be a constant fluid feed to both power steering cylinders, while starving the main hydro unit. When the float spool gets bumped, it creates enough back pressure to get the tranny speed back to normal. I will be checking the bypass valve in the near future. I don't suppose anyone has pictures of what this looks like on the real unit by chance? I found some schematics in a Sunstrand service manual, which I think is Item D on page 24/28 found here: http://inspectapedia.com/heat/Sunstrand_Txmsn_Manual.pdf. Any thoughts?

JDS
 

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Jason,

If bumping any of the three hydraulic control levers gives a transmission speed response, the bypass/relief valve would seem to be the problem. Here is a jdparts diagram of the implement control valve assembly used on later 400's. Parts 1-5 make up the bypass/relief valve. The assembly is physically mounted under the tractor about 180 degrees from the appearance in this diagram. In other words the bypass/relief valve slotted cap will be in the lower front corner. It is a tight spot and should be cleaned well first, but the cap can be accessed under the tractor without pulling the whole assembly.
Harold

jd400newervalve.jpg
 
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