Discussion in 'Mechanic and Repair' started by 70stang, Jun 16, 2007.

  1. 70stang

    70stang LawnSite Member
    Messages: 6

    Just purchased a used 1999 MDDGHS with a little ov 1000 hours on it.
    Thrid time I did the lawn (great job) I noticed a oil slick on the lawn when I was almost done.
    Checked out tractor found main PTO gear box, empty and dripping oil on floor.
    Removed mower and I can clearly see a crack on bottom front corner of box.
    Now interesting this PTO Box looks new (nice and clean)and the I found two of the four bottom mounting bolts to be loose.
    Could this have caused the crack?
    Is this a common problem?
    Now what is the trick to removing this gear box from the tractor?
    There seems to be no room to get this thing out?
    Do I need to remove the blower or the hydro & wheel drive gear?
    Can I purchase just a new case?

  2. tomo

    tomo LawnSite Senior Member
    Messages: 660

    hello, pto box damaged cracked leaking etc
    ?Is the pto box u have, the earlier version [u can identify if it has a traditional slip on triple groove pulley ]
    The later box has a bolt on triple groove pulley .
    Apparently the bolt on pto box can be removed out the sideafter pulley is removed
    Removing the earlier pto box requires at least blower removal . I personally own a MT unit gaser . It is very easy to remove engine on this model .

    If u own a diesel ghs unit the rotation is opposite to the MT ghs .Then there is the non ghs models .If u order part out side of dealer make sure u have correct part no . U will also need the upgraded pulley

    The earlier pto casing halves are not available any more .This is a decision from walker as the only places these boxes come from is walker .They are made for walker by american gbox company .

    Loose pto mounting bolt is caused by to many objects being hit in the grass ,this causes a shock load in drive train even if the unit is equipped with shear pins . Make sure these r all in good order eg proper specs not high tensile bolts etc

    VIBRATION via drive shaft
    Secondly is the slip joint in the drive shaft have only minor play or is it trashed
    Thirdly The quick release coupling on the end of the pto out put shaft .
    On the mating surface splines are they worn causing even minor play . This is another cause of damaging vibration .

    The quick release coupling is a crap idea as it is spring loaded . When the vibration starts the coupling vibrates on the adjoing spline causing major wear and potential damage to other parts such as loosening of the mount bolts

    This is the most heavy duty box that the american g/box company has in this series

    As with other g/boxes on walkers and other machines that use this brand they r not heavy duty enough

    Problems with the pto box in walkers is not un common and in the extreme cases bolts will all come out and the box will smash itself to deathand other components .

    One can only hope that hydraulic drive to deck is more common in the future .
    Nothing wrong with pto system when built properly .!!

    The casing halves do not like being removed and over hauled to many times as the bolt hole areas r VERY VERY WEAK they eventually get hairline cracks

    If u o/haul cases and they donot require repairs [metal putty etc ]reseal them with
    loctite sealant for alloy cases 508 or 510 or512 checkup ,if u use the incrrect type it will leak eventually .The correct type allows 4 flex in the alloy under load

    tomo:waving: :waving: :drinkup:
    ps the mount can also crack where pto mounts

    Have i ever had issuses with the pto box'' you bet ya''
  3. 70stang

    70stang LawnSite Member
    Messages: 6

    Thanks for the reply.
    I have the latter gear box with three bolts holding the drive pulley groove belt.
    I will try removing the pully and see if I can get the box out the side, still looks tight.
    This is my first walker and have only owned it 3 weeks.
    I think it will be my last.
    I have used old BOLENS ( no longer mfg) equipment since 1966, they have the same spring loaded quick coupling drive shaft-- however they made there own gear box with CAST IRON cases. I never had a gear box issue even when cathing rocks in the snowblower and hitting roots with the mower. Broken blades, bent augers YES, but never a PTO or drive train issue.
    I am very sad to see such a nicely designed tractor have such a poor PTO design.
  4. tomo

    tomo LawnSite Senior Member
    Messages: 660

    If u choose to rebuid make sure the dirt slinger [looks like an extra seal] is located on the out put shaft . If u run without this the output seal faces the front where all the grass debris is flying around and dirt etc will get under seal causing leaks .
  5. 70stang

    70stang LawnSite Member
    Messages: 6

    I checked the shafts from the main PTO gear box to the mower center gear box.
    Not sure which one is bent but whenthey are coupled there is a large bend, a good 1/2 in the center.

    So now I plan to order new Main PTO gear box and both shafts to the mower.

    Started disassembly, had a lot of trouble getting shear pin out of shaft on mower end. Now I cannot get the shaft off the mower gear box shaft.
    Will not budge.
    Shouldn't this just pull off?
    Any idea?

  6. tomo

    tomo LawnSite Senior Member
    Messages: 660

    the shaft that is attached to the pto output shaft has a quick release coupling .If u push the collar [a thin large washer either forwards or backwards it releases the spring loaded ball so u can remove coupling ]The only other reason this will not come apart is if the splines are binding from excessive wear[generaly it does become a looser fit ]

    please buy a manual for both parts and service 4 your model . These will be a huge help for becoming familiar with your machine and importantly it also has some specs that will be important . EG pto belt tensioner adjustment
    and hydro motor tracking adjusment procedure

  7. 70stang

    70stang LawnSite Member
    Messages: 6

    I know the shaft connected to PTO is a quick release coupler.
    I have that side off.
    I talking about the shaft that connects to the mower center gear box.
    The side with the shear pin.
    I had a lot of trouble getting the shear pin out, finally got the pin out and now I can't the drive shaft (which is bent) to pull off from the Mower gear box shaft.

    I have the manuals, it just shows pulling the shear pin and the shaft sliding off.

  8. tomo

    tomo LawnSite Senior Member
    Messages: 660

    there is 2x pins u need to remove from the yoke . [one end takes uni and other fits onto input shaft ,female hole ]
    One pin u remove is the saftey pin which fits not to tight in most cases.Although it can deform making it difficult to remove . Its function is to transmit the drive . It installs thru one side of yoke then thru the shaft and thru the other side of yoke .From memory a split pin is installed once installed

    The second pin actually retains the yoke on the input shaft to deck box in the advent u breakthe shear pin. This must be punched thru also . Difficultto explain on web . Once u have apart u will see
    A groove is machined in the deck input shaft [around the shaft ]
    The ""retainer pin"" enters the side of yoke and passes thru the grooved are a and back out other side of yoke . When u pull on the yoke it pulls the pin up against groove machined into input shaft .

    Once apart the yoke should fit on the input shaft without to much slop.
    When they have reasonable play shearpins can break more often [components work on ythe pin ] Generally if there is a heap of play it has broken many pins . The wear is caused by the yoke spinning on the input shaft.

  9. lucforce

    lucforce LawnSite Member
    Messages: 223

    I have to disagree on the gearboxes being "under-designed." If it looks like a shiny part as mentioned, then I would assume that it has been replaced. This is the case, I would then assume that it was not properly installed (loose bolts). At only 1000 hours on the machine, I would further assume that the machine has not been properly maintained and serviced. I say this because the Walker will live with the original gearbox much beyond 1000 hours if maintained. Additionally, we can not really say that the machine was well maintained if there are parts falling off of it.

    That said, you will have a hard time locating the bare cases. You would just about have to find someone that is parting a machine out.

    Your shaft must be rusted in the splines.
  10. tomo

    tomo LawnSite Senior Member
    Messages: 660

    hello, industrial gearboxes
    have dowels locating both casing halves
    bearing preload by shim adjustment etc
    casings are not typically made from alloy or at least when they are have 3/8 inch thick casing
    better mounting bolts that pass thru casing to sandwich box to its mounting
    The pto box fearures none of the above :hammerhead: :hammerhead:

    quick release coupling although good idea in practice this is where the problem starts .Coupling needs to be held firmly on shaft but still easy to remove . A spring loaded ball does not hold coupling firmly

    Universal joints and the bearings in the pto are at max rpm of the specification listed by there makers .Running a unit at 100% does not encourage long life

    The shiny situation u r talking about can also be caused by excessive oil leaks washing case alloy .Common when bad oil leaks r present .

    On machines that ""have not"" seen regular maintenance pto box [including the drive to deck components ] failure and excessive wear and tear is common .

    Late model cases available from walker or complete unit either walker or aftermarket suppliers

    The same with the gasers i have seen engines fail at 6oo hrs also although not that common, engines failing at 1000hrs is typical if maintenance is poor

    If maintenance is important as 70 stang is discovering it cannot be underestimated with a walker .


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