I am looking at possibly buying a komatsu pc78 at an auction soon. The one I am looking at has steel tracks with street pads. The pads are in really good shape and don't look to be that old, but the chains are toast. There is actually wear holes in some of the links at the pins. So I know for sure that it needs chains and sprockets. I am not very experienced at undercarriage evaluations, but the rollers and idlers looked to be in pretty decent shape no real noticeable major wear. I am buying this as a farm machine that will only see 150-200 hours a year tops. Is it possible that I can get by with just the chains and sprockets or is it more likely that the whole undercarriage will need to be replaced. I am hoping I can get by with just chains and sprockets because the idlers and rollers are going to be another $2500-$3000. the machine has 5500 hours on it.
Others may disagree, but for a home/farm use machine I would replace just the chains and sprockets, then just worry about rollers and idlers if and when they fail or get worn beyond practical use.
Thanks lantraxco. That's what i am hoping I can get by with. Also I just noticed that one of the final drives has some oily residue at the face of the drive. Right were the face plate meets the sides of the drive near the plug holes. I am wondering if the residue is just from someone checking the drive oil or if there is a seal leaking there. Like I said its up at the face of the drive not back behind the sprocket like I have seen in the past. Thoughts?
If they'll let you, check the oil level in both drives. If it's a lot low, and/or the color and smell are bad, might be best to pass, though sometimes it's just lack of maintenance. There's an O-ring that seals the cover, it may be seeping slightly, or there could be some internal pressure forcing oil out. If the oil is overfull and thin, there's a hydraulic leak into the planet side, again, pass. Might be a minor problem, might need major work. YMMV
Here is a pic of the residue if it helps anyone diagnose the problem. Unfortunately I don't think the auction company is going to let me pull the plugs to check the fluid.
Ahem.... You sure it's not leaking back behind the sprocket as well? That's not a little seepage, that's an ugly leak. I'm guessing at one of two scenarios, either it's gear oil and the drive is low or empty, or the more likely in my mind is that hub is full of hydraulic oil. OR, oil is seeping out of the center of that one plug, why is it clean and the other two are packed solid? Hard to say without pulling a plug.
Looks to me to be seeping on the face plate. My guess is that someone was in there at one time is didn't get the faces completely clean before applying the ackenpucky and sticking them back together. The sprocket doesn't look that bad but I can see the track pins through the bushings. A photo of the bottom rollers sitting on to of the chains would let us know how bad the rollers are and whether or not you need to think about them.
I'm a little curious why there is no oil on the track pads...... I would think a leak like that would have some oil residue on the pads.
We have similar size machine to that, and it sweats oil in same place. I've not seen a drip, and the levels stay correct through 500 hrs, I checked regularly when it started appearing 1000 or so hrs ago. It's a lot less than that picture, but anyhow, it doesn't drip. Yet. By the cleaned out plug, the levels inside might not be representative now. Could have a few tools and a rag in your pocket on viewing day, though?