Lubrication Related Failure???

Some of you may have seen the thread on the failure of the final drive on my KX91-3....https://www.heavyequipmentforums.com/showthread.php?21644-Kx91

Below is another picture of the parts with a ruler and pen for size comparisons. The parts are aligned how the are assembled in the drive - the male end of the gear drive goes into the female end of the shaft. The worn male splines are clearly visible, the female splines look the same. The splines wore out at 1765 hours. The other side failed at 1400 hours (but I did not have to replace that one, it was done before I bought the machine, I also don't know exactly what parts failed in the drive unit, I was just told it was replaced) The rest of the gears and bearings in the failed drive look fine - no visible wear on most of them.

The shafts are tiny, just under a 1/2 in diameter. I understand the final drive gears are a torque multiplier, but still its hard to believe that the entire motive force starts with these small shafts.



These parts are in the deep center of the drive unit and in my guess receive very little direct lubrication. My guess is the design and gear oil played a factor here? Comments?

I've switched from the Kubota 85W-90 gear oil to AMSOIL SEVERE GEAR® Synthetic Extreme Pressure (EP) Lubricant 75W-140 hoping the full synthetic oil would provide better cushioning.

Tony

I think it is more likely design, maybe some shafts leaving the factory were not heat treated properly. Do not rule out previous owner abuse, you start loading up the drive train by pushing alot of dirt, to often and then those 1/2 shafts start to look kind of small. Were you able to source the part with female splines?

Nm the last question

Such small parts providing so much power!!

The previous owner(s) may have tried to do a lot of turning whilst in 'high speed' mode which as we know the machines don't like hence putting the splines under a lot of pressure.

It's a known problem with this brand.
We actually have our own, improved, design shafts made for us.
We cannot supply all of them yet. But we see this failure all the time with this brand drive.
Plain and simple it is poor design.

I think it is down to poor tolerances in the manufacturing, to much play in the splines from the start! A local machinist has told me of a similar problem with a certain brand of truck mixer grearbox!

I talked to our local dealer and they found it is a hit or miss with the failures. They have seen one side go at 1000 hours and the other side last for 2500 plus and still going, and some people no issues. One would think it is a metal treating problem with some shafts, but it could also be poor design as well, as said by final drive.

Tony_F
Did you see any metal in the oil when you changed the shafts? I change my oil twice a year and run a magnet through the oil and have never found anything. I have thought about installing a plug with a magnet on it to give a heads up to failure. Any thought on where a person might find a magnetic plug.

Brian

nobull1 said:

Tony_F
Did you see any metal in the oil when you changed the shafts? I change my oil twice a year and run a magnet through the oil and have never found anything. I have thought about installing a plug with a magnet on it to give a heads up to failure. Any thought on where a person might find a magnetic plug.

Brian

Click to expand...

No help on a plug, one can probably fabricate it with a mill, round magnet and a little epoxy. There is not much clearance between the internals and the cover, so whatever is used it can not protrude much into the drive.

I did not see any metal in the oil when I first changed it after I bought the machine (a few months ago.) I did notice a tiny hint of silverish color, I ran a magnet thru it, but it did not pick up anything. So I didn't think much of it. My guess is that the fine particles would take a while to stick and build up to anything noticeable on the magnet. Same thing when I drained it to repair it, no chunks, which is the real reason I decided to attempt a repair, I assumed if it was a catastrophic failure, there would be some pieces in the oil.

If the cover wasn't such a pain to remove, it would be simple to pop it off and visually check the internals every now and then.

When it failed there was no warning, that side just stopped turning and started making a high pitched whining noise. I was able to limp back to the trailer, but for the life of me I could not get it to climb the ramps on the trailer, (fell off twice) had to call my son in law who is a skilled operator to come rescue me.

I'm planning on changing the gear oil again in the spring. I'll post back the results when I do as well.

Tony

Kinda surprised that the high dollar machines of today don't come with chip detectors.
http://www.tedecoindustrial.com/electric.htm (as an example)
just one more light on the christmas tree.

I wonder if sending an oil sample when changing the oil might give a heads up to a coming failure before it leaves a person stranded?

My machine (A Takeuchi TB25) broke a retention clip, and that broke a tooth, and that broke a tooth.... It happened when the guy that owned it before me used it to grade a road in high speed..... On the bright side, I bought the machine cheap.....

http://www.youtube.com/watch?v=0zzMoKiGJ3g