John Deere 717a Tensioner bolt

[OldNSlowMow]

I have searched the WWW high and low and can not find anyone else who has had this issue. In the past month I have had to replace the tensioner arm bolt 3 times as it shears off at the nut. Its a huge pain as it has to be torched to melt away or lastly used a hacksaw blade and pair of vice grips.
Part Number
19M8977

2nd time I thought I didnt have the correct washers so I replaced all with OEM parts. The bearings are a little stiff but still roll. I replaced all parts but bearings today and the bolt broke again. I do hear a whoorling sound every three or four blade rotations.

 

[OldNSlowMow]

 

[bertsmobile1]

Thanks for posting the screen shot, it makes things a lot easier .
Unless JD got a bad batch of bolts, I can not see why the bolt would shear.
I presume part 28 is wither a grease seal or heavy washer and part 10 is a spacer .
AS JD kindly give you dimensions I would be inclined to go to my friendly nut & bolt merchant and get a grade 9 socket headed cap bolt ( allan bolt to some ) and some M8 high tensile washers.

make sure when done up tight the spacer gives enough clearance for the arm to swing freely without binding and that the pivot is greased.

 

[OldNSlowMow]

One thing I dont understand is why there isn't a washer on top of the bearing. Part 28 is the bearings, shouldn't there be one between the cap bolt and the bearing? There is on the bottom and then a large washer(spacer).

 

[bertsmobile1]

In theory there should be on there to stop the arm from moving up unless the tube has a step in it so the outer race of the top bearing holds the assembly down
You can put one in if you like just make sure it has clearance so the assembly can rotate without hanging up on the washer.
If this deck came into my workshop, that is how it would be going out

 

[OldNSlowMow]

Thank you for the reply, to me it seems the flange on the top bolt over laps the inner race and would benefit from a washer. I also know John Deere diagrams are pretty much spot on so I didn't know if that 1mm difference would cause a issue. There is room for the washer no problem, I will add that and see how it does.

 

[OldNSlowMow]

Mowed about 15 hours since adding top washer and checked bolt. So far so good!

 

[OldNSlowMow]

Still going strong, reckon that top washer is needed.