MX 5/6/7 John Deere gearbox solution found

   #1  

brown40

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Dec 29, 2010
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493
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Maine
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JD 3520
Good Morning All,
Finally received the comer LF 227j gearbox yesterday.
A number of people have shared their disappointment with JD after purchasing the MX series of rotary cutters, because output shafts break predictably, and the company version of "support" requires purchase of a new gearbox and stump jumper for at least $2200 (have seen higher quotes even), basically railroading the customer into buying a new cutter.
For years the design used a retaining bolt, which terminated about 0.375 inches from a 90 degree snap ring shoulder, which created the condition, was not abandoned until their recent change to a castle nut configuration, which leaves the steel intact.
I need to open up the ~0.75 bolt hole up to 1.25 inches to accomodate the COMER LF227J gearbox; at that point the gearbox will be a bolt on replacement. It requires some work to do:

opening the stump jumper hole by 1/2 inch
and either
a) drill 6 new 0.80 holes in the reinforcing steel bowl that sandwiches the upper and lower decks together --or--
b) cutting the reinforcing bowl out,drilling the 4 spot welds out from the top, rotating it 30 degrees, and welding it back in place.

I chose b) to keep the steel, and have the bowl as a drill guide for the top sheet metal.

My solution was expensive for me, because I didn't own a welder... here's the math (not counting my time!):

Setting up for welding (I chose Lincoln MIG/flux 180 dual) $1100.00 (& accessories)
New 20 spline slip clutch driveline $275.00
COMER LF227J 1.69:1 gearbox $550.00
So I'm up to $1925.00, but have the welder, plus an extra 21 spline slip driveline (anyone need one?), but do not have the bonus stump jumper/scrap metal JD's fix would have left me with.

I still have warranty on the box & driveline, which is fine: I had zero support on the unit anyway.

If you have (or hire) a welder, the fix would be less than half what JD is demanding to fix their OBVIOUS design flaw.

I am pleased to have had this occur, because now I have a welder, which I'm getting to know (if you are thinking of a MIG welder, the 230V/higher voltage is the way to go-mine does both, and it's night & day the difference on heavier materials (like 0.375), but I will find small projects for sheet metal I'm sure that need the lighter touch of 115V), and have now got chain hooks on the pallet forks, hitch receivers on the bucket & box blade, and the capacity to do work I had to hire out before. To date I've only used the flux core, because everythings heavy gauge I want done.

It would have been very costly for JD to retrofit all the MX series with gear that wasn't on a countdown to catastrophic failure... x% of future business versus y% of retained customers= ???. Must have been worth it to see a% new cutters sold, b% retrofit old cutters, and lose z% of future equipment sales.

I'll post pictures when it's done; the gearbox will NOT be painted green!

There is a fix, it's not an easy bolt on fix, but when you see the comer on the MX... looks like putting a 7.3 liter into a fiesta-- kind of comical, yet reassuring.
 
  
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#3  
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brown40

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Maine
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JD 3520
Well it's definitely not just a matter of bolting it on; have to remove more material from the bottom of the stump jumper & radius the hole shoulder in the hub spline and see how close that gets me to the hole on the castle nut... the original bolt was over 3 inches, and the output threads are only 2... committed now so will resolve then document.
As far as bolt pattern & length to output shaft spline, its right on the money.
Its important to note I have "version 1" of the stump jumper, with the 1"x 4" bar stock straight across the bottom of the hub/top of the jumper, where version 2 had a redesign that seems it would be more easily mated to the comer. I began with 1.375" of steel and 1/2" gap from the spline end to the steel start.
The stump jumper is wide and heavy compared to some others I've seen, and must transfer a lot more shock. It definitely does not lend itself to being retrofitted with a castle nut, but it will be licked!
 
   #4  

Ken

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North Central Arkansas
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One of the easiest fix is to buy at lessor cost a Bush hog Brand cutter. maybe any other brand would do.
Then put up 4 posts and then stack the MX6 on top for cover
reliable equipment should be protected from the elements.

ken
 
  
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#5  
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brown40

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Maine
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JD 3520
That patented MX double deck would provide many additional years of rust-free shelter compared to similar cutters!

It is all back together, and working better than ever (new blades have been hanging for years are on it, but old ones still aren't halfway worn out). I do have to take the slip clutch completely apart on the new shaft--its's painted together pretty good and wouldn't slip on anything light & I won't push it until I know those disks are polished up/working correctly.

After working on it, it really is a great design (the MX); castle nut from the start instead of that tapped output shaft and they'd be as good as they were (are) billed to be.
 
   #6  

bushhog28

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nc
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Massey 5611
One of the easiest fix is to buy at lessor cost a Bush hog Brand cutter. maybe any other brand would do.
Then put up 4 posts and then stack the MX6 on top for cover
reliable equipment should be protected from the elements.

ken

lol!! I'm bush hog shopping now. BH27 might be heading my way.
 
   #7  

Ken

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North Central Arkansas
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John Deere 4520,
When I'm getting JD parts or oils for my 4520 I make sure that he is reminded of the MX6 problem then tell him that he will loose the next tractor purchase .
Used to be friendly He now disappears when I come in the front door. So I sit and talk to the parts man more than planned .

Thought of just loading a other brand tractor on trailer. then stop in front of the dealer. And go in just for a cup of the coffee and talk to parts man for awhile.
ken
 
   #8  

chevyls6

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May 12, 2011
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JD 1050
Any pictures of this fix? I'd like to try something with my MX6...
 
  
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#9  
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brown40

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493
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Maine
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JD 3520
Hey All,

Sorry about not getting pictures up sooner. Thanks for reminding me.

Unfortunately I have no pictures of the cutting and reconstruction of the deck reinforcing bowl. For those that aren't staring at one--it's a steel bowl--about the size of a medium kitchen bowl with six holes drilled in it. It's 3/8 inch thick and is continuously welded to the lower deck on the rim of the bowl.

4 tack welds hold the drilled bowl 'bottom' to to the upper deck. The gearbox bolts to the bottom of the bowl.

Note the 60 degree shift in bolt pattern between the new black comer box and the busted green deere one. One could drill six new holes and accomplish the same thing--it would leave very little steel in the bowl, which seems to be the heart of the double deck design.

The bowl depth is what makes replacement an issue for the MX series.

The comer 227 specs match the dimensions of the failed gearbox bottom--i.e. the steel bowl depth between the decks.

It took a lot of modification to the hub to get the castle nut seated, and the long term durability remains to be seen.

It is intact, it runs fine so far--time will tell!


IMG_0203.JPGIMG_0208.JPGIMG_0208.JPGIMG_0205.JPGIMG_0206.JPGIMG_0207.JPGIMG_0208.JPG
 

Zebrafive

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I agree on the cut, reposition and reweld verses drilling 6 new holes that size (not easy to drill large holes by hand).
 
 
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