Ideas please? I have a 1997 kobelco sk120 that is having a final drive issue. The machine will track forward and reverse but however the left side track will not turn the machine. It is like it is weak or binding but again it works fine when using both tracks forward or backward. Also when you track at full speed the machine will begin to veer off from straight travel. I am hoping that it is a reasonable fix as I just bought the machine. Help please.
Most likely a bad seal in the swivel joint that carries the hydraulic circuits between the upper and lower sections. Could also be bad relief valve, weak motor, etc.
when you say weak motor aare you referring to the drive itself or the hydraulic pump? I failed to mention that multiple functions are not a problem as I have operated the turn table while tracking and operating the boom and bucket. The only issue is not being able to spin the tracks opposit each other when turning the machine. My primary concern is the possibility of trashing the entire drive by continuing to operate until my mechanic can make the repair. Thank you for the wicked quick reply!!!
Yes, weak hydraulic motor in the drive itself, as you didn't mention any related weakness of any other function. First bet would be the swivel seals. Might want to drain a bit of gear oil out of the final drive housing, see if there's metal in it, how black it is and what it smells like, but doesn't sound like a gear issue right off.
If I remember right, that machine has separate travel relief valves from main relief's. They are mounted in the main control valve near where the main hyd pump hoses go in. Switch them to see if the problem follows the valves. wes
I really appreciate the advice fellas. I will try both of these suggestions today and get back with you with results. Very much appreciated.
After some investigation the relief valve at the pump had an adjustment. I have turned the valve a flat and a half and the pump has picked up significant strength. Still not equal to the other but will work under a load. It will still bind at moments and make a hammering sound but if you engage the other track and pull forward or backward and retry it will turn freely. Also I have found an sk130 that is the same year. To you knowledge are the pumps, drives, cylinders, ect. Interchangeable? The engine is the same for sure. Thanks again for all of you help.
Check what comes out of the gearbox
Trying to upload a photo for clarity, but the gears looked new. Absolutely no ware and very little play. The teeth are seated well and no shavings. The oil had a little milky appearance but that was probably from tracking it right before disassembly. It did not smell burnt and had good viscosity.
I am certain at this point that it is hydraulic but am lost at how to diagnose it. We have climbed all over the machine while listening to valves and breaking lines loose to see which lines supply which valve for function. We did remove a stem from a valve today that the line that goes to the track was connected. The stem looked fine. What I assume is a relief valve we also disassembled and it was clean and so we then adjusted it to add pressure "probably a mistake" I was not a fan of this as I'm not sure that increasing fluid to a motor that seems to be bypassing is gonna help. This is what I adjusted. It seemed to help As the whine got quieter and the track began to function. This was shot lived as a couple minutes later it began to struggle again but notably less than before adjustment was made. It is significantly stronger backing than going forward. Thanks to everyone for the advise. This has no doubt been a huge help so far. I had rather spend time checking leads than throwing money at a problem and not find a solution. Thanks Jared.
Upon taking the case drain line loose I have discovered that the case drain port on the pump is barely letting oil leave the pump but the line instead of matching this function is pressurized and is pushing hydraulic oil into the case drain. I have suspicion it is now the swivel. The only problem is that the case drain lines "T" together below the swivel so I assume that the functioning track also has this failure. It functions properly. I have ordered the seals to rebuild the swivel but highly doubt that this will cure my problem now because of the "T". Is this a reasonable assumption since one side works with the back pressure and the other isn't? Thanks Jared