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JD400 Reverser - No Forward

12702 Views 27 Replies 6 Participants Last post by  Mattharter
Reverser on my JD400 Industrial is malfunctioning. Works in reverse, does not do forward. Checked hydraulic pressures at forward tap and reverse tap on reverser control valve. Pressure is good on reverse pressure tap, there is almost no pressure at all on the forward tap. As clutch is nearly released, see pressure creep to maybe 3-5 psi, then feel a small "bump" then jumps back to zero. I have just changed hydraulic fluid and both filters - all checke done per tech manual SM-2074. Where is most likely place to find problem?
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The only connection between the brake valve and reverser is that the brake valve is filled with oil from the reverser valve. Applying brakes has no effect on reverser. I am assuming the tractor moved forward before the engine and clutch rebuild? Have you considered possibly the sealing rings(#2a or 2b second diagram)on the forward clutch pack may have gotten damaged when reassembled? If you d remove the reverser valve, be careful of internal oil lines that connect to back side of valve. They can come out of place and splitting between clutch housing and transmission housing is required to get them back in. See items #4, 6, 8, 9, and 10 in first diagram. Of course one of these lines could be cracked or split causing the problem also.


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I don't recall ever seeing a failed piston in a reverser clutch. Maybe one or two in other applications, but not in a reverser. That's not to say it's impossible. I'm not sure I follow your logic in the use of the aluminum plate. If you achieve pressure when the oil is restricted going out of the valve, I would think that is evidence of the valve working properly. I would think a cracked line would be more likely. There has to be a sizeable leak to have zero pressure.
It has been a long time since I have been into one of these. We had a customer once that removed the valve and dropped that forward tube and we were not successful in reinstalling it until we split the tractor between the clutch housing and transmission housing. You mentioned in an earlier post that there was less resistance in forward when you applied air pressure to it, so I think you are correct that the problem is in that line, or it could be in the forward clutch also. I have never tried using a scope to see into the housing, but that coud be a possibilty. Back when I worked on these last, we didn't have a boroscope, but they are definitely a handy tool if you have access to one.
There is no need to split at engine/clutch housing. You can split at clutch/transmission housing first.
Glad to hear you are back in action. That reverser should give long service. They are typically very durable.
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