older 331 swing motor carrier- BIG problems

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nepondguy

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Jun 7, 2012
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Hi gang. I have an older 331 (1999ish). The other day i heard a crunch and then lost all swing ability. Having replaced the swing motor years ago I assumed that the gears had all broken off. I tore it all apart yesterday and found a much bigger problem. All 8 of the bolts that hold the carrier to the machine were broken or stripped out. Clearly it had been like this for awhile. Replacing the housing and replacing seals and bearing while it is apart is just time and money. My bigger concern is how do I best fix the actual frame? Drill out and rethread with larger bolts? through bolt? Has anyone dealt with this before? Anyone in upstate NY want a project?? Thanks in advance for any and all help!
 

Tazza

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Never done it myself, but i'd replace the broken bolts and if you can, drill the worn out ones and re-tap them larger. You could possibly install heli-coils, but that will cust a fair bit.
 
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nepondguy

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Never done it myself, but i'd replace the broken bolts and if you can, drill the worn out ones and re-tap them larger. You could possibly install heli-coils, but that will cust a fair bit.
Yeah that is what I am thinking. THe bobcat dealer here was not much help. Basically told me I am screwed and will cost me an absolute fortune. I power washed it yesterday to see what I am dealing with. I agree the best bet seems to be to drill everything out larger and use larger bolts with a ton of locktite!
 

Tazza

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Yeah that is what I am thinking. THe bobcat dealer here was not much help. Basically told me I am screwed and will cost me an absolute fortune. I power washed it yesterday to see what I am dealing with. I agree the best bet seems to be to drill everything out larger and use larger bolts with a ton of locktite!
They just want you to replace the broken parts with new ones so they can be sure it will work. With people being sued so easily these days, they may not like giving advise that could leave them liable?
Either way, i think yours should do the job.
 

mmsllc

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Dec 29, 2015
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They just want you to replace the broken parts with new ones so they can be sure it will work. With people being sued so easily these days, they may not like giving advise that could leave them liable?
Either way, i think yours should do the job.
It sounds like the bolts were never put back in place as tight as they should have been; remember loose bolts break / wallow out holes. However, I would only use "case hardened" steel bolts. I would use a "case hardened" nuts, too; if you decide to through bolt it back together. They will cost more money, but easily worth it. If you step up to larger / stronger bolts, I think that is another good call. Just remember to tighten them to their specific torque spec. I hope bolts are all that you end up needing. Best of luck to you.
 

7LBSSMALLIE

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Feb 2, 2012
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It sounds like the bolts were never put back in place as tight as they should have been; remember loose bolts break / wallow out holes. However, I would only use "case hardened" steel bolts. I would use a "case hardened" nuts, too; if you decide to through bolt it back together. They will cost more money, but easily worth it. If you step up to larger / stronger bolts, I think that is another good call. Just remember to tighten them to their specific torque spec. I hope bolts are all that you end up needing. Best of luck to you.
yea its me so I got say it part of daily inspection is look for loose or missing bolts. should felt it before it got to this point.. but yes it is repairable. theres two ways to do this one at a time from uderneath . or go big and lift the house off and do it right really aint that bad done it both ways. as for labour the time saver seems to be. split the house from the undercarriage and do it right. even if youre goining to helicoil etc. now you got access..
 
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nepondguy

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Jun 7, 2012
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yea its me so I got say it part of daily inspection is look for loose or missing bolts. should felt it before it got to this point.. but yes it is repairable. theres two ways to do this one at a time from uderneath . or go big and lift the house off and do it right really aint that bad done it both ways. as for labour the time saver seems to be. split the house from the undercarriage and do it right. even if youre goining to helicoil etc. now you got access..
It is tough to inspect these bolts as they are buried deep in the machine so inspection would require removing a few panels and the seat. Regardless, i believe I have figured out how this happened. This mounting assembly was replaced about 10 years ago. It looks like the alignment pins were not put back in at that point. Those pins are nonexistent and the holes look untouched. So that being said the bolts had to clamp it as well as hold the rotational force. Clearly over time they failed. I will try and post a picture. It seems like I should be able to drill and tap from the top and then use heli coils or larger bolts. Wish me luck!
 

mmsllc

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It is tough to inspect these bolts as they are buried deep in the machine so inspection would require removing a few panels and the seat. Regardless, i believe I have figured out how this happened. This mounting assembly was replaced about 10 years ago. It looks like the alignment pins were not put back in at that point. Those pins are nonexistent and the holes look untouched. So that being said the bolts had to clamp it as well as hold the rotational force. Clearly over time they failed. I will try and post a picture. It seems like I should be able to drill and tap from the top and then use heli coils or larger bolts. Wish me luck!
if the alignment pins are missing, then that could have a huge impact on the bolts working themselves loose. It sucks that they were not put back in, but as long you get it right this time it wont matter much as time rolls by. be sure to grease the grease fittings for the swing / slewing bearings. as long as you only have replace bolts, I think that is the best scenario possible. I am not sure about using heli-coils, though. I think using larger bolts might prove to be a better idea.
 
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