PTO driven snowblower keeps shearing pins

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YooperJD60

Member

• Jan 10, 2019

• #1

I keep shearing a pin on the snowblower and can't figure out why. It doesn't take much of a load in the blower and It shears. At first I thought maybe I was going too fast,but even at slower speeds it shears. The blower seems to operate well otherwise. I can rotate the shaft by hand and it feels smooth and easy.

 

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Bob

Well-known Member

• Jan 10, 2019

• #1

Over time the shearbolt holes get wallowed out/tapered, so the shearbolt gets pushed on unevenly, making it break much easier than when the holes are straight and true.

 

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YooperJD60

Member

• Jan 10, 2019

• #1

That could be the case....the shear pin is 1/4" and fits loose...maybe I should drill it out to 5/16" or drill a new hole?

 

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DIM

Member

• Jan 10, 2019

• #1

I had that problem on my snow blower. I had repaired the drive shaft and did not weld the u joints back in line.

 

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old

Well-known Member

• Jan 10, 2019

• #1

I would drill out the hole it already has to the next size up and give that a try unless the shaft is real small

 

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rrlund

Well-known Member

• Jan 10, 2019

• #1

.

 

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Roger in Iowa

Well-known Member

• Jan 10, 2019

• #1

Was the original a special bolt? Should not fit loose. Was the original a metric bolt?

Drill new 1/4" holes, both pieces.

 

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YooperJD60

Member

• Jan 10, 2019

• #1

It also has a keyway...does this sound right? When the shear pin breaks then the PTO shaft keeps spinning or flys off and I also lose the keyway

 

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stevob671

Member

• Jan 10, 2019

• #1

So is it supposed to have a key and the bolt is just to hold it from sliding off? Do you have a parts diagram you can refer to or dig up online?
If you got the make/model handy maybe someone can come up with more info also.

 

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kevinj54

Well-known Member

• Jan 10, 2019

• #1

(quoted from post at 18:05:05 01/10/19) It also has a keyway...does this sound right? When the shear pin breaks then the PTO shaft keeps spinning or flys off and I also lose the keyway

Click to expand...

Sounds like your shaft is too long.

You need to post some pics of this, I do not think you are looking at a shear bolt.

 

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Leroy

Well-known Member

• Jan 10, 2019

• #1

A shear bolt would NOT have a keyway in shaft as that would defeat the reason for the shear bolt, A shear bolt would shear from turning and a key would not let it do that. You have to be having a push-pull problrm rather than a rotation problem.

 

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YooperJD60

Member

• Jan 11, 2019

• #1

I have no idea what the make/model is....I'm going to be working on it tomorrow..I'll take some pictures.

 

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rustyfarmall

Well-known Member

• Jan 11, 2019

• #1

I would drill a new 1/4" hole. A 5/16" shear bolt might not shear easily enough to protect the rest of the machine.

 

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Michael Soldan

Well-known Member

• Jan 11, 2019

• #1

Any PTO driven device will shear pins if the pins do not fit properly in the hole designated for the pin. Others have it right, drill both pieces of the PTO shaft to uniform diameter and put in a pin that fits.

 

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Bob Bancroft

Well-known Member

Location

Aurora NY

• Jan 11, 2019

• #1

Is there a keyway in both the shaft and the yoke? Do you have a key in there? Usually there's a set screw to keep the key in place.

My sprayer has a 5/16" bolt which holds the yoke on the pump. There is also a set screw. Every once in a while the bolt disappears. It has done this since day one, when I bought it new.

 

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Ken Macfarlane

Well-known Member

• Jan 11, 2019

• #1

Thats not the shear bolt, that bolt is to keep the yoke from walking off. We had the same problem on our blower. We locktited the yoke with key onto the gearbox. Installed the set screw with locktite too. Installed the bolt with some locktite too.

Took the shear bolt flanges apart and freed up the seized bushing where the actual shear bolt was located. With new grade 2 shear bolt the shaft no longer came off the gearbox but would shear in the correct place and spin on the bushing.

 

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johnwayne360

Member

• Jan 13, 2019

• #1

i had this trouble a couple years ago. put blower on new bigger tractor with bigger rear tires. if i run the blower level on that tractor,
it will put the pto in a bind and shear a pin. if i tip the blower back and down, it works fine.

 

495man

Well-known Member

• Jan 13, 2019

• #1

If there is a keyway you shouldn't be breaking that pin.

Chances are the keyway is toast now.

The right way to fix it is get the shaft and yoke repaired ($$$$) the cheap way is to put the key back in and then put a bolt in and use a LOCK nut , tighen the nut up so the bolt can't slide in and out, but can still turn. Yes this will continue to ruin the key way and shaft but if you weren't going to fix it right it doesn't matter.

I agree with the others, check your PTO shaft length and find out if you aren't breaking that pin due to another issue.

Also, fine the REAL shear pin and take it apart and clean, make sure everything turns free with out a pin in it.

 

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YooperJD60

Member

• Jan 15, 2019

• #1

(quoted from post at 13:13:05 01/11/19) Thats not the shear bolt, that bolt is to keep the yoke from walking off. We had the same problem on our blower. We locktited the yoke with key onto the gearbox. Installed the set screw with locktite too. Installed the bolt with some locktite too.

Took the shear bolt flanges apart and freed up the seized bushing where the actual shear bolt was located. With new grade 2 shear bolt the shaft no longer came off the gearbox but would shear in the correct place and spin on the bushing.

Click to expand...

Thanks so much for the advice!! You were exactly correct! I found the actual flange with the shear bolts and it only had one bolt in it...it was seized together. Got that freed up and loctited everything at the gear box.. I used it for 3 hours on Saturday and not one problem!