It's a poor design in my opinion. Too many pieces are in the shaft and are pinned together. Here are the pieces just to make the short shaft from the rear of the hydro to the bearing assembly that the pto is mounted to.
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Here is what the shaft looks like. The pins wear the couplers so that the holes get egg shaped and then the shaft hole gets worn and the pin gets loose and the safety wire is the only thing holding it in place.
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I have purchased all new couplers from Surplus Center but the one that attaches to the rear of the hydro is splined on one end and needs the other side machined out for the short shaft. I have talked to Jeff about this a year or so ago but never went any further.
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I often wondered why the shafts couldn't be welded or at least leave on pin in just incase you hit something and needed a shear pin