Rockshaft housing, explosion

[erisque]

Recently had my 4300 in for repair of rockvalve, had less than 50 hrs on it. When it was returned, the rockshaft control lever was so hard to move, it could barely be used. I figured it may loosen up with use. Went to do a job, as I worked, it got harder and harder to move. Finally I backed into a small sand embankment to cut it down, I was going to make a backwards cut first, then pull it forward. As soon as the box blade made contact "low speed" the whole rockshaft housing exploded!! Does anyone have any idea whether this could have been caused by faulty installation of the previous rock valve? It seemed to me, "prior" that this piece would have been indestructable, in my opinion, "should be". I may submit a post later w/ picture of damage, I apologize for multiple posts, but am hoping someone with same nightmare may see this and shed more light, please, anyone with simular experience, "TELL ME!!!". After repair, I am leaning towards bigger machine, this one has less than 100 hrs, 5x repaired so far

 

[kubmech]

erisque, check out "Three point fatigue" in Kubota owning, may shed some light.

 

[erisque]

Hey, I read the 3 point fatigue issue, although I was not aware of this, it doesn't really seem to apply to myself "in this instance". I was grading with the boxblade when it occurred, I was attempting to push through the top of a mound of sand as my box would not raise over it, I did not even apply that much pressure, actually it did not occur until I started pulling forward to re-align. I am always careful to not let the box drop. Also, not just internal components broke, the whole housing broke. I could see internal components breaking, but I am totally befuddeled how the housing could break. This part should be strong enough to endure almost any situation, short of running it into a block wall. I truly feel, this is a case of poor engineering, as I stated earlier, the back side has no fastners, especially at the bottom, which is a gasket mating surface and is not further strenghtened by another side running at a 90 degree angle, it is aprox. 1/4" thick on the flat portions surrounding the connecting points which I truly feel is inadequate. I have encountered another person who also broke his housing, "brushhogging", they did cover his under warranty, I only hope I'm so lucky. I will post a picture tomorrow so everyone can see what I am referring to. If you have never held one in your hand, or seen one broken it is probably hard to picture, Thanks again

 

[kubmech]

Just wanted to relay "simular experience" as requested. The "fatigue" post mentions rockshaft housing breakage as well as internal damage that can be caused under some circumstances. Kubota requires a reinforced top link bracket when installing a 3pt mounted backhoe which prevents the back of the rockshaft housing from ripping off due to the extra stress created at this point. The extra leverage that a rear mounted implement places on this point does not require what seems to be excessive force to cause damage. In the scenario you have described (hitch at full raised position, pulling through a load) could have caused this stress. Did it crack on the back stroke and break away on the pull stroke? I don't know, just offering a possible cause for your failure. Should it be able to handle this stress? Of course it should. I personnaly recommend the reinforced top link bracket for all applications (not just backhoes) on the Kubotas. I don't recall the older John Deeres requiring this option and I really don't know if the new ones do. In the 7 years I worked on Deere's I saw a few of these. On Kubotas I've seen more than a few on the newer machines, ballpark? probably 15 in the last two years, even had one that ripped the back of the differential housing out as well as the back of the rockshaft cover. None, with the reinforced top link bracket installed. All the machines I have repaired with this failure, were covered under warranty without any hassle to the customer (other than the machine being down). I would be very suprised if you ran into any problems with your repair being covered under warranty.The previous repairs you mentioned may also have been a player in this event. It sounds like the friction adjustment may have been too tight for the lever, which is most likely two jam nuts compressing a set of spring washers and if that was the case it's doubtfull this contributed to the failure, however if they missed that adjustment, who's to say they got the feedback link adjusted properly which could cause the hitch to be "bottomed" out at the top constantly applying hydraulic
pressure (instead of kicking the lift valve to neutral) causing undo stress to the rockshaft assy. Just a thought/w3tcompact/icons/smile.gif (not a slam)/w3tcompact/icons/smile.gif
if the controls did'nt feel right after the machine was repaired I'ts always a good idea to have the dealer take another look at it, rather than continue to use it.
I don't think you're going to have any problems getting it covered under warranty./w3tcompact/icons/smile.gif

Kubmech