Broke lower pulley bolt, WHY?

[MrIQR]

Snapped the lower pulley bolt for the second time.

10.9 grade bolt both times

I was running pro pulleys, going back to stock axys now that the lower is destroyed.

why does this happen?

what can I do to prevent it?

bearings were fresh.

 

[J270wsm]

10.9 is a metric bolt and is basically the same as a grade 8 bolt.
What sled?

If I remember correctly this was an issue with some pro rmks and Polaris addresses this issue.

 

[DKP]

Get the ARP bolt, locktite and torque proper....... The threads are way to far in the shaft IMHO. leaving much bolt to flex if it gets at all loose. So much belt tension it constantly flexes bolt back and forth with every rotation. If it's loose, OR, there is play in splines, this exacerbates it leading to failure at the first thread. ARP bolt is like grade 12 or better. Also, loctite bolt, BUT, but a little anti sieze on the washer to bolt and washer to pully surface. Just a tiny bit. To allow any flex to happen at outside of bolt.

 

[MrIQR]

2017 Axys 155 800. I believe Polaris’s fix was the 10.9, originally they were a 8.8.

 

[MrIQR]

The bolt in it was the “upgraded” bolt from zbros which is a 10.9. I loc-tited and torqued it to spec.

And Yes. The threads are in way to far. The bolt broke(again) where the threads end inside the shaft. Maybe I should Heili-coil to extend the threads out? Couldn’t hurt right? Would help spread the load..

good idea in a touch of anti-seize.

where do i get the arp bolt? Is it a 12.9?

 

[Teth-Air]

It is not the fault of the bolt. It is the design. The driveshaft is too short. It does not extend out as far as the belt so it tips the gear on the shaft on every rotation. This tipping continually could be controlled by a strong non-flexing bolt but there is a second movement of the gear on the shaft that undermines the bolt. The gear splines are often loose on the shaft so as you accelerate the gear pulls to the back side of the shaft splines. Now you brake and the gear rocks to contact the front of the splines. This repeats over and over 1000's of times and the gear is grinding back and forth under the head of the bolt, slowly wearing some clearance. Now if you don't retorque regularly, this clearance increases and once again allows the gear to tip on the shaft as it rotates. The tipping of the gear works under the head of the bolt, bending back and forth repeatedly until it fatigues and breaks.

So if you can stop the gear from moving on the splines it will not loosen the bolt and then it will not fail. (even a cheap bolt) This is difficult but adding Loctite 660 to the splines helps a lot. Some guys got lucky and the gears already fit tight on the splines but others are terrible. Now, as nothing is a perfect fit, a good good bolt helps and regular torqueing is required. If you find it loose, it would have failed.

On my 2015 the gear was really loose on the driveshaft. I drilled the bolt hole larger and tapped the hole. I applied Loctite 660 on the splines and then I threaded in a grade 12 stud with red Loctite. I double nutted the gear on with blue Loctite. This was an easy fix and gave me confidence it was not going to fail.

So how did Polaris try to fix this? The newer sleds got a deeper hole and a new bolt that had a shoulder. The shoulder is thicker than the threaded area so the gear would flex this stronger, thicker area. Does it fix the problem? No, but it will reduce the problem as the bolt does last longer before breaking. Remember some sleds are good and some sleds have sloppy splines. The sloppier, the quicker it will fail.

Now you know, there is no excuse for this to happen again.

 

[MrIQR]

What exactly do you mean by “double nutted”?

I will tap it larger this time and add some retaining compound like 660, hadn’t thought of that.

 

[Teth-Air]

What exactly do you mean by “double nutted”?

I will tap it larger this time and add some retaining compound like 660, hadn’t thought of that.

A stud has no bolt head. I used 2 nuts locked to each other to hold on the gear. The stud I made by cutting off the head of a socket head bolt.

 

[MrIQR]

Ohhh, duh, I read-over the stud part.

I’m about to tear mine down and see how bad everything looks. Was dusk when it broke and well after dark by the time we got it towed out.

 

[Teth-Air]

Ohhh, duh, I read-over the stud part.

I’m about to tear mine down and see how bad everything looks. Was dusk when it broke and well after dark by the time we got it towed out.

Hope it works out well for you. The take-away for everyone should be that regular checks on the bolt torque will usually avoid losing the gear and brakes at the same time. Secondly, if the gear is looser on the axle you are a prime candidate for problems if you don't take care of the issue.

Chris

 

[AdrenalineAddict]

I haven't actually measured but some have a spline/sprocket excess clearance fit, these will continue to fail as your sprocket rocks back and forth with every revolution. Some sleds have a much tighter spline/sprocket fit and will likely never fail. I'm not sure if the the sprocket splines are machined a little larger or smaller batch to batch or if the driveshaft splines are smaller or larger batch to batch. I solved my problem by going to the 10.9 and replacing the convex washer with one that wasn't so flat, I locktited it in at only 20 ft/lbs. in an effort to maintain some elasticity in the convex washer, has worked for 2,800 miles.

 

[ullose272]

Get the ARP bolt and be done with it. Summit racing has them, there is another thread if you search it will give you exact specs its something like a 12x1.50 x60 or 65 mm.

Sent from my SM-G973U using Tapatalk

 

[Teth-Air]

Get the ARP bolt and be done with it. Summit racing has them, there is another thread if you search it will give you exact specs its something like a 12x1.50 x60 or 65 mm.

Sent from my SM-G973U using Tapatalk

Not true. The bolt will still loosen if the gear is rotating slightly back and forth under the head. That is a function of the splines and not the bolt.

 

[ullose272]

Not true. The bolt will still loosen if the gear is rotating slightly back and forth under the head. That is a function of the splines and not the bolt.

Maybe, but the likelyhood of the ARP bolt breaking is far less.

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[ullose272]

If you want to try some different pulleys i have the stockers off my 21 id sell

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[LPIdaho]

Most likely the pulley splines are not tight enough to the driveshaft.

 

[Tewstroke]

It is not the fault of the bolt. It is the design. The driveshaft is too short. It does not extend out as far as the belt so it tips the gear on the shaft on every rotation. This tipping continually could be controlled by a strong non-flexing bolt but there is a second movement of the gear on the shaft that undermines the bolt. The gear splines are often loose on the shaft so as you accelerate the gear pulls to the back side of the shaft splines. Now you brake and the gear rocks to contact the front of the splines. This repeats over and over 1000's of times and the gear is grinding back and forth under the head of the bolt, slowly wearing some clearance. Now if you don't retorque regularly, this clearance increases and once again allows the gear to tip on the shaft as it rotates. The tipping of the gear works under the head of the bolt, bending back and forth repeatedly until it fatigues and breaks.

So if you can stop the gear from moving on the splines it will not loosen the bolt and then it will not fail. (even a cheap bolt) This is difficult but adding Loctite 660 to the splines helps a lot. Some guys got lucky and the gears already fit tight on the splines but others are terrible. Now, as nothing is a perfect fit, a good good bolt helps and regular torqueing is required. If you find it loose, it would have failed.

On my 2015 the gear was really loose on the driveshaft. I drilled the bolt hole larger and tapped the hole. I applied Loctite 660 on the splines and then I threaded in a grade 12 stud with red Loctite. I double nutted the gear on with blue Loctite. This was an easy fix and gave me confidence it was not going to fail.

So how did Polaris try to fix this? The newer sleds got a deeper hole and a new bolt that had a shoulder. The shoulder is thicker than the threaded area so the gear would flex this stronger, thicker area. Does it fix the problem? No, but it will reduce the problem as the bolt does last longer before breaking. Remember some sleds are good and some sleds have sloppy splines. The sloppier, the quicker it will fail.

Now you know, there is no excuse for this to happen again.

Would a small section of splined shaft (cut from a previously failed driveshaft) help as a spacer on the end of the shaft?

 

[Teth-Air]

Would a small section of splined shaft (cut from a previously failed driveshaft) help as a spacer on the end of the shaft?

There is no clearance for more shaft length. If the shaft was longer then the splined section in the gear would then need to also be lengthened but then I doubt you would be able to get the axle into the sled.

 

[gtwitch]

it would be interesting to try several different gears on the splined shaft to see if it is the splined shaft or the gear that is loose on the splined shaft. I have put the PRO gear down on my 18 AXYS 800 and my sons 18 also and used new ARP bolts with no problems in two years of tough tree riding , I did find no play, slack or wiggle in the fit from the gear to the splined shaft when I did the install of the gears.

 

[Teth-Air]

I put my video of the slop of the stock QD2 gear from my 21 Khaos on to Onedrive. Hope the link works.

https://specifiedtechnicalsales-my....VPtBRYNzzPA30BWWuk4uGoEXOYh-e3-SnCbQ?e=bd5fgc