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Old 08-06-2023, 01:34 PM
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SlimJim SlimJim is offline
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Default Cat 420 slop

Hey guys, I am working on the cat 420 I borrowed 20 years ago and still have. I basically fix things on it and when the owner ever needs it he comes to my barn and drives it out knowing it’s greased, running well, and full of fuel and all other fluids. It’s good for him because he may need it once or twice a year and it has not been sitting out in the weather without running at all. It’s good for me because he may not need it even that often. Also, I am not in construction with it but just use it around the farm. So a good deal for both of us. Having said all that, before he retired he used this 25 year old machine every day. So the bucket and boom have more slop in it than you can imagine. If you swing and stop, it don’t! Also I know nothing about the backhoe except for what I have learned from manuals and posting. I noticed there are big gaps where their should not be, places where more of those giant washers or shims could be three times more. And that their are bushings I could knock out. Where would you start? Replace pins, bushings etc? Or disassemble and post pics?
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Old 08-06-2023, 01:42 PM
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"Or disassemble and post pics?"

The last line in your post.
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Old 08-06-2023, 02:02 PM
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It probably depends on how much time, work and money you want to put into it.

From what you say about swinging and not stopping, it sounds like the hydraulic swing cylinders are bypassing internally, if it has cylinders to swing the boom with.

You can probably just start fixing the worst joints, first, and see if that helps get it into a useable condition for you.

Are you able to make bushings and pins yourself, along with welding capabilities? You might be able to tackle a lot of these repairs yourself, otherwise it might cost quite a bit of money to get them fixed by a mechanic.


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Old 08-06-2023, 02:51 PM
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If the slop is from wear and tear, the bores that the bushings go in may be egged out or oversize.

Equipment bushings are not something I would try to make. Generally with Cat equipment, it’s about .001” interference per inch of diameter. So a 4” bore will have about .004” interference.

If you go to replace bushings, be prepared to find either liquid nitrogen or at least dry ice to re-install them. I’ll see if I can find any bore specs for it, what specific model is it?


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Old 08-06-2023, 07:43 PM
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I have dumped LPG inro suiyable container to cool things to -40 C or F to shrink for instalation. cheep and easy to find.
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Old 08-06-2023, 07:58 PM
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Since you are not trying to make a living with it you have time and just pick off the major offenders.

Dad had a machine that was sloppy like that, and was a cat 215 excavator. I believe I have the number correct.

We extended the bucket out as far from the machine as it would go. shut the machine off with the bucket off the ground and I pushed on the bucket back and forth and Dad picked out where he wanted to start replacing pins and bushings.

He picked out the biggest offender and we started there. Fixed that one and made a world of difference in the slop, That was the only one and the last big project we worked on before he passed away.

Scott
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Old 08-07-2023, 01:56 PM
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Good to see you post up Jim. Hope your leg is acceptably better...

I think if you could post pics or a vid of the "slop" that would be a start. Places like the worn pins and what not. I'm not anywhere near an expert on fixing slop as these other guys are but I would start with what I could easily move by hand--you know, the real big gaps. If you can find/feel slop by hand, I'm sure a hydraulic piston is going to exacerbate that slop...
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