Keep breaking shear bolt on drive axel - Snowblower Forum : Snow Blower Forums
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post #1 of 11 Old 01-24-2020, 04:13 PM Thread Starter
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Keep breaking shear bolt on drive axel

Snapper snowblower model 1694993. Earlier this winter, the drive cable was noticeably loose. So loose that it the friction disc didn't make contact at all, so there was no drive at all when the lever was engaged (forward or reverse). At the same time, the shear bolt on the drive axle broke. I replaced the shear bolt with a "standard" snowblower shear bolt from menards (not the exact part replacement) and adjusted the drive cable by tightening it two notches. When tightening one notch, it still did not drive at all. Fast forward a month and the machine has broken like 5 or 6 different shear bolts. The part number is 720220. Does anyone have any ideas as to why this machine keeps breaking shear bolts? Could the drive cable be too tight causing extra strain on the drive shaft? If that is the case, I'm assuming I need to replace the drive cable? because loosing the cable to the next notch is still too loose and will not drive.
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post #2 of 11 Old 01-24-2020, 05:18 PM
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If you have a damaged/wobbly shaft in the chain maze inside the trans case. Don't only look at the shaft where the bolt goes through the sprocket, look what's hooked to that shaft via chains. I have seen more often than not machines that use these type "bearings" which I just call wobble bushings. I personally think they are a sloppy fitting for tolerance errors. If the shafts working together don't stay parallel things can get torqued wrong.
Other thing is you could just have a sharp edge either in the shaft or sprocket the bolt goes through.

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post #3 of 11 Old 01-24-2020, 06:02 PM
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From what I can see it's not a shear bolt, it's just a long shouldered bolt that's been superseded to : Snapper 704212 BOLT, HEX,1/4 20X1.75
I don't see any reason for it to be a shear bolt. During operation the wheel should slip against any surface before you could do any damage to anything.
If it was my machine I'd get a similar grade 8 bolt for that application. Shouldered would be great but threaded if not.
Only reason for shear bolt in the auger is to stop power to the auger if something becomes jammed in it. That doesn't really apply to the wheel drive.

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post #4 of 11 Old 01-24-2020, 06:15 PM
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As mentioned, that is not a shear bolt on the drive axle you should not be breaking those wheel bolts on the drive axle if that is what you are referring to.
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post #5 of 11 Old 01-25-2020, 07:09 AM
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[QUOTE=oneacer;1716209 you should not be breaking those wheel bolts on the drive axle if that is what you are referring to.[/QUOTE]

yet it very possible as i have found out many times, to shear off even grade 8 bolts, when the holes allow side to side slop, toro has a set of the 1/4x20x 2 inch bolts,spacers and lock nuts ,where the hole in the axle is larger than the wheel , they bang back and forth ,side to side, reach a point and snap off falls the wheel
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post #6 of 11 Old 01-25-2020, 07:48 AM
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Well if you have that much slop in the wheel, I would fix it by cleaning it up and sleeve that axle hole and get the appropriate size bolt/lock pin.

I have never broke an axle bolt/lock pin where it goes through the wheel in my life, on any machine.
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post #7 of 11 Old 01-25-2020, 01:53 PM
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The Snapper parts manual shows a Klik-Pin for the wheels. That's whats on All my Snappers. Although I agree, Never broke a bolt on any machine that held on the wheels.


GLuck, Jay
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post #8 of 11 Old 01-25-2020, 03:14 PM
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I subbed in a grade 8+ bolt (yes they exist) for my auger when I was out of shear pins one time.
The shear pins from the mfg lasted much longer.

Grade is a designee factor for clamp, not side shear.

True shear bolts are treated for the side stresses.

Still if its breaking in that app, you have another problem.

1998 YT624 Have Owners and Service Manual, Rubber Disc Drive (not hydrostatic)
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post #9 of 11 Old 01-25-2020, 03:25 PM
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Quote:
Originally Posted by oneacer View Post
Well if you have that much slop in the wheel, I would fix it by cleaning it up and sleeve that axle hole and get the appropriate size bolt/lock pin.

I have never broke an axle bolt/lock pin where it goes through the wheel in my life, on any machine.
taught the same,only there isn't enough meat to drill to 5/16. and not weaken both , the axle hole is some odd size i have yet to try and size with drills, just know it is not anywhere near what it should be to be snug,

never had that issue with a powershift that used a simple hitch clip to hold a wheel on

for a note
if one wishes to get not so easy to find grade NINE bolts i found them, Nutty Bolts
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post #10 of 11 Old 01-25-2020, 03:52 PM
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Hheheheh . breaking a grade 8 takes a lot, let alone a 9 .
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