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420 Hydro won’t work

1311 Views 3 Replies 3 Participants Last post by  Town Manager
Good afternoon,

I was mowing my lawn today after having finally finding the time to put the deck on. Tractor was operating normally when the hydraulics suddenly surged. The tractor just took off at a high rate of speed. I tried to brake but it overrode the brakes. I pulled the lever back to reverse and it still moved forward. It finally came to a stop and now it will not move forward or backward. I will tow it back to the shed after supper and start disassembly next week.
Any thoughts or advice? Thanks

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I guess there could be a lot of things that could cause this. My first thought is the roll pin in the swash plate lever broke or fell out. Can't say I've read of that happening to anyone on the forum, though. It is common for the pin hole to get worn badly and or the bore of the lever can get worn. As that happens there will be noticeable creep, or difficulty finding neutral with the hand control. Hopefully it will be something repairable in the operating linkage and not an internal problem.
Removing the fender deck will be the best way to check the lever and that part of the linkage. Pretty sure JD still has this part available, but it is a bit pricy!
Let us know what you find when you are able to work on it.

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The swash plate is the only thing I can think of also.

Pull the pan and check the linkage.

I think I have a couple pumps in the shed if you end up needing one.
Tom my hawk and rydplrs,

My problem turned out to be fairly simple. There is a 5mm bolt that ties the linkage together below the 3 bolts that had backed out. Replaced the missing nut and we were back in business. I appreciate your getting back to me with valid solutions. I really need to pull the pan and examine the linkage at the transaxle as I think I have some slop there. Thanks

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