My gray-market Cat 307SSR is chronically sloppy at the offset-boom knuckles...I'm sure life's not been kind to them, and my long-term plans include dealing with this. But since I've only got a parts-book (and it's in Japanese), I can't really grasp how these are supposed to be serviced. Can anyone advise as to whether doing so is perchance a "custom-machining-free" process, eg one that might, say, just require that I drop/drive out the heavy hollow-pin-bearings, somehow remove a bushing or bearing that rides outside it, press in a new one, and replace the thrust-bushings, in order to get back to a tight joint? The heavy lifting/support during disassembly is something I believe I can manage, but it would sure be nice to get a sense of what the rest of the process is going to be, before I get into it too far. I'm also wondering: how likely it is that the pins are OK, with all wear taking place on the bushings? Getting the parts from Asia (etc) isn't going to be cheap. Are there any similar English-language r&r processes written up somewhere? Mahalo - Dave
Bushings, dust seals, thrust washers (#27, As Required), hard pins. No real mystery there, except are you sure that's where the slack is? If it will twist some, or has some fore and aft slack when you push down on the boom and then lift up, then yeah it's worn. Could be though you have vertical slack that just needs some shims or thicker thrust washers, or if the front part of the boom moves back and forth sideways you might need to look more closely at the cylinder and the parallel rod on the side. just a thought. Unless the bores are hammered out it should be a relatively straightforward job of replacing bushings and/or pins depending on the amount of wear.
Thanks Lantraxco - you raise a good point; I can't just jiggle it around by hand and be up close to see where the play is...would be nice to get away with only changing out thrust-washers (#27, as you noted). What might look like solid pins in the parts-book (#3, #17) are actually like heavy-wall pipe sections, and I'm guessing expensive & heavy to ship, in my case from Asia, or... Anyway I'd been hoping they would be magically fine, with all the wear being on the bushings, but I guess this is all speculation and I'll have to pull things apart to know. They appear to be kept from falling out of their bores by simple cross-bolts. Do you figure those bushings will drive out with an ordinary BFH, no special tool or portable press-type device required? --Dave
A few random thoughts; On a high hour machine, wear in the pins as well as the bushes is almost inevitable. The vertical hollow pins will have been exposed to the weather and may be rusted in to their bosses so badly that they need to be cut out. On the other hand you may find that the grease has prevented rust and the pins have instead worn into their bosses. Almost any bush can be easily removed with the carefull use of a cutting torch. Getting the new ones back in can require a little more thought.
If the ID is big enough, you can run a weld bead or two on the inside of the bushing, when it cools it will fall out. Same effect can usually be had by heating with an acetylene welding tip inside the bushing, a couple lines from end to end red hot and let cool. I have split them with a cutting torch.
Good tips, thanks Lantraxco. I will let you know how it goes... --Dave
Cmark, thanks...that reminds me of how accumulated rainwater pours out of...well, something...in these joints. "rusted in badly" sounds like par for the course in my environment, although the water that drains out doesn't look nasty-rusty, so yeah, maybe the grease is helping. I guess I need to evaluate how serious this problem is, vs. just an OCD-annoyance; I think it comes with the territory for some of us who are into machines to also want things to be "just so." If I knew that the pins were about to wear through the bushings, well, I'd consider that an emergency, as would be the case if I had so much play at the bucket that I couldn't complete certain tasks precisely enough (hah!) or safely. It just won't stop raining here - at least the third summer it's been like this - so regardless, it's probably a terrible time for me to get into another "tent in the mud" repair that goes on for weeks while I ferret out parts and ask for help with diagnosis...