Chain Drive Problem... - Snowblower Forum : Snow Blower Forums
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post #1 of 42 Old 10-26-2014, 01:48 PM Thread Starter
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Chain Drive Problem...

I'd like to ask for advice and information reference a problem with the final drive chain that keeps jumping off the sprockets on a Sears/Craftsman model C950-52712-7 snow blower. I'd like to know how others have rectified this problem on these types of machines and what would be the most reasonable course of action.

I read that the chain might likely be worn or stretched so would installing a new chain be best option or can the chain be shortened to give it a tighter fit on the sprockets? I tried shortening the chain one complete link but that made it too short to fit. I understand that a chain can be shortened by just one 'roller' and I'd like to know if anybody has successfully tried that.

Also, looking at the compete wheel drive assembly it appears that the drive chains run on an 'offset' in relation to the driving and driven sprockets. I want to ask if this is by design as I've seen this mentioned on other web sources and there doesn't seem to be any bent or twisted shafts or sprockets that would account for this otherwise?

Any help or advice would be most sincerely appreciated. I want to avoid the bother and expense of completely replacing all sprockets, shafts and chains if it isn't necessary.

Many thanks...
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post #2 of 42 Old 10-26-2014, 02:51 PM
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When you say offset, do you mean the 2 sprockets the chain goes on do not line up perfectly straight with each other? If the chain is going crooked it is going to jump off. You have to figure out why it isn't lining up.

Most chain systems have some way to tighten the tension I would thing. I know there is a nut in my Ariens I can loosen to pull the sprocket further away and adjust the chain tension. Obviously if the chain is too far gone tightening it won't help. I have heard as chains get stretched over time they don't fit on the sprocket gears correctly.

You could try a half link if you think that will work. I have heard of people doing that. Also it will probably be cheaper to buy bulk chain and make your own vs buying the specific chains from Sears.

Lastly (or more like firstly) make sure all the spockets are tight. Check for play and wiggle in the bushings and bearings holding those to the shafts and the shafts to the frame. Also make sure the frame isn't ripped where the shafts are bolted to it.

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post #3 of 42 Old 10-26-2014, 03:42 PM Thread Starter
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Originally Posted by Shryp View Post
When you say offset, do you mean the 2 sprockets the chain goes on do not line up perfectly straight with each other?
Yes. The chain path is not parallel with the associated sprockets yet there is nothing that looks bent or twisted. There's also a 'jack shaft' forward of the axle assembly (for drive gear reduction) that looks like it was intentionally mounted on a strange angle. Even the frame looks to be square.

I've seen other people making comments on this who noticed the same thing on their machine so that's why I'm asking if it is designed that way.

This Sears blower was apparently manufactured by 'Murray' so perhaps someone who has seen the drive set-up on a Murray snow blower can shed some light on this...

Last edited by Autolite; 10-26-2014 at 03:46 PM.
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post #4 of 42 Old 10-26-2014, 03:57 PM
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I would say something is wrong. There is no reason those gears should not line up. That is just asking for trouble. Here are some Murray snowblower repair videos if you want to look up and see if anything matches yours.

https://www.youtube.com/user/donyboy...h?query=murray

Which chain is giving you the trouble? The one around the wheels or the one around the friction disc? I would guess the wheels since you say "final drive chain". Are your axle bushings nice and tight?

Just for the heck of it maybe pull the bolt out of that sprocket and make sure it isn't bent and that someone didn't drill a new hole in the axle. Make sure the wheels are tight and there is no left-right movement in the axle. Maybe try some spacers and a file or something to bring that sprocket back center with the jackshaft sprocket. Just make sure the jackshaft is good before altering the axle.

Is your jackshaft supported on both sides or only the one side? It might just have bearings completely shot. You might not be able to tell until you remove both chains.

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post #5 of 42 Old 10-26-2014, 04:01 PM
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It may be the angle that the picture was taken, but are all the shafts parallel to one another. The reason that I ask, the top shaft, in the picture, appears to be slightly higher at the left hand side.

I don't own a Murray, just observing what's in the picture.

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post #6 of 42 Old 10-26-2014, 06:18 PM Thread Starter
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It may be the angle that the picture was taken, but are all the shafts parallel to one another. The reason that I ask, the top shaft, in the picture, appears to be slightly higher at the left hand side.
No, the shafts are not parallel with each other but there doesn't seem be be anything bent or twisted. It appears that they were built that way. I know that it doesn't make sense and this is what has me baffled. If the frame is bent, twisted or buckled, I'm just not seeing it!

I've emailed Murray technical support and I am hoping that they can explain it. Also, I've found out that the 'jack-shaft' was replaced from being worn out in 2002 and the final drive chain was replaced in 2009. I'm guessing then that this isn't the first time this machine has had this problem.

I'm starting to wonder if there's been some sort of manufacturing defect with this model...
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post #7 of 42 Old 10-26-2014, 06:20 PM
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Type in Partsandservices.com, and search for Murray, and you should be able to find your model #. I had very good luck with this site, finding a '95 model and the diagrams were very helpful. My model did not have "repair" links on the chains. so I replaced all three chains. Murray manuals are just about impossible to get.Good luck. The older Murrays were good machines. Yeah you have something going on there, all those shafts should be parallel to each other. Good luck.
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post #8 of 42 Old 10-26-2014, 06:46 PM Thread Starter
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Originally Posted by Shryp View Post
I would say something is wrong. There is no reason those gears should not line up. That is just asking for trouble. Here are some Murray snowblower repair videos if you want to look up and see if anything matches yours.

https://www.youtube.com/user/donyboy...h?query=murray

Which chain is giving you the trouble? The one around the wheels or the one around the friction disc? I would guess the wheels since you say "final drive chain". Are your axle bushings nice and tight?

Just for the heck of it maybe pull the bolt out of that sprocket and make sure it isn't bent and that someone didn't drill a new hole in the axle. Make sure the wheels are tight and there is no left-right movement in the axle. Maybe try some spacers and a file or something to bring that sprocket back center with the jackshaft sprocket. Just make sure the jackshaft is good before altering the axle.

Is your jackshaft supported on both sides or only the one side? It might just have bearings completely shot. You might not be able to tell until you remove both chains.
Thanks for the advice and the video link. I'll check it out. The problem is with the (final drive) chain that runs around the axle for the wheels.

I'm thinking that perhaps the next step is to just disassemble and inspect everything in the drive line. I know that someone has had it a part before so maybe something wasn't put back together quite right...
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post #9 of 42 Old 10-26-2014, 06:51 PM Thread Starter
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Quote:
Originally Posted by Sid View Post
Type in Partsandservices.com, and search for Murray, and you should be able to find your model #. I had very good luck with this site, finding a '95 model and the diagrams were very helpful. My model did not have "repair" links on the chains. so I replaced all three chains. Murray manuals are just about impossible to get.Good luck. The older Murrays were good machines. Yeah you have something going on there, all those shafts should be parallel to each other. Good luck.
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Thanks, but I already have the manual. This is actually a Sears Craftsman blower that was built by Murray so getting parts lists and diagrams doesn't seem to be much of a bother...
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post #10 of 42 Old 10-27-2014, 10:18 AM
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The large sprockets almost never wear out, the small ones will after a long while. I think it's an alinement problem. You should be able to sight along the chain, or the large sprocket by eye ora small straight edge to check the alignment.
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