# Keep breaking shear bolt on drive axel



## Jwmiller39 (Dec 31, 2019)

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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## oneboltshort (Dec 16, 2019)

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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## Kiss4aFrog (Nov 3, 2013)

From what I can see it's not a shear bolt, it's just a long shouldered bolt that's been superseded to : Snapper 704212 BOLT, HEX,1/4 20X1.75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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## Oneacer (Jan 3, 2011)

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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## 2.137269 (Nov 15, 2019)

oneacer;1716209 you should not be breaking those wheel bolts on the drive axle if that is what you are referring to.[/QUOTE said:


> 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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## Oneacer (Jan 3, 2011)

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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## JayzAuto1 (Jul 25, 2016)

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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## RC20 (Dec 4, 2019)

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.


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## 2.137269 (Nov 15, 2019)

oneacer said:


> 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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## Oneacer (Jan 3, 2011)

Hheheheh …. breaking a grade 8 takes a lot, let alone a 9 ….


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## 2.137269 (Nov 15, 2019)

went out last night, the wheel is drilled 17/64 a 1/4 bolt shoulder just a slight tad loose, the axle is drilled 19/64 . don't see enough meat to drill both to 5/16. 

as to why they shear ? take into account all of the back and forth, side ways movement on a 1/4 inch shaft, the side torque applied when shifting forward and reverse, or using the power steering. (which to me seems to be when it happens) all that slop banging around, on a bolt that uses a spacer to take up the extra unneeded length, that never feels tight ,why is the inner end of the spacer right where the thread ends at the thinnest point of the bolt, right at where the wheel OD sits, something will give at some point ,


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