Fanshaft support pedestal on 620 tractor
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Thread: Fanshaft support pedestal on 620 tractor

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    Fanshaft support pedestal on 620 tractor

    I need to install the fan shaft support on my 620 JD tractor. The shop manual cautions against messing with this at all. (My guess is that the gear alignment at the governor is affected). Too late, the support has been messed with. Now how do I reinstall it properly? There were some thin washers (shims) between the main case and the support, but not as many as indicated in the parts book. Any insights or tricks of the trade will be welcome. Thanks in advance.

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    Keeper of the GTT Cookies dieselshadow's Avatar
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    Thumbs up Welcome to GTT!

    Which shop manual do you have? eBay has a couple of vendors who have reproductions of the original service manuals, owners manuals, and even a collection of all the manuals for about $50. I highly recommend getting the combination manual. It's very complete and has everything the dealer mechanics had at their fingertips when repairing these tractors.

    I suspect you need to set the backlash correctly with those shims. Too little backlash could destroy/damage the ventilator pump, governor, and associated bearings. Too much could be very noisy.

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    I just checked my 60 parts book and shop manual on the fan shaft. They don't show any shims on the front support for either the power steering or the non power steering units, altho mine had a couple in there. All the heel and backlash setting on the bevel gears on the governor end are set with gaskets, either at the ventilator housing or on the governor drive gear. When I reassembled mine I shimmed it just so I couldn't feel any binding in the vertical plane of the fan shaft. Seemed to work as I have no noise coming from the gears. There may be more to it on a 620 but in my experience with bevel gears is they are set with shims / gaskets on the gear shafts for proper mesh and mercy there are a passel of them on a 350 desmo Ducati.

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    All I can recommend is the manuals, as others have.

    But...

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    Thanks to all who have responded.

    The two manuals I'm using are the common old "IT Service manual" and the "John Deere Manual for Dealers". SM-2025.
    I also have a 620 parts catalog.

    The IT Manual paragraph 11 simply says "CAUTION: Do not lose the shims located between the fan support and the tractor frame."

    The John Deere Service Manual says " NOTE: Do not disturb the location of the front fan support on the tractor frame unless absolutely necessary as this establishes the proper alignment of the fan shaft assembly with the governor case."

    That's the only reference I can find in the manuals.

    The parts catalog indicates 8 washers (part # 24H 1343) between the fan support and the tractor frame.

    To my way of thinking, these washers are really shims used as needed to to achieve the proper height of the fan shaft's forward end. If the fan shaft were to droop even slightly, a strain would be placed on everything all the way back to the governor. Too many shims would have the opposite effect and the fan tube and shaft would strain upward.

    So… the question remains, how many shim washers do I use to insure the correct height of the fan's forward mounting?

    When I dismantled the tractor, there were only 2 shim washers and they were both on the same leg of the support. I could simply duplicate that, but how do I know if that's what the factory determined or if it was due to a careless re-build by a previous owner?

    Thanks in advance for any help.

    Bob

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