4wd Carraro King Pin Failure

Something that is often asked of me by people who own a Case backhoe is what should they be keeping an eye on before it costs them a major repair bill.

One of the most common issues is a lack of greasing the king pins on the front axle. On both 2wd & 4wd models, this can create a huge problem if not maintained properly.

The problem is that the lower bearing is a lightweight design & when it goes wrong – it causes a great deal of damage.

This problem exists in the 580/590 K, SK; SL; SM; SR fitted with the Carraro front axle. Given time & circumstance the lower bearing race fails & metal fragments slowly destroy the machined bore for the bearing cup in the main axle – which is clearly marked with the phrase “Ductile Iron – Do Not Weld”

Once the main housing is worn it will not retain the bearing cup & so a major repair is required to correct the situation.

To make things right, the axle must be completely stripped down to a bare housing – involving removal front axle from the machine, removal of both steering trunnions, axles & diff centre. Then a machine shop will weld the worn housing & bore the bearing location while aligning the top bearing location to allow a precise fit of the lower bearing cup.

This usually creates a small panic on the jobsite when the amount of TIME involved to carry out such a repair is discussed – before even mentioning the COST!

Notice also the term “weld the worn housing” – can that, should that be done on a housing that clearly tells you NOT to weld it?

In short, yes!  Ductile Iron CAN indeed be welded using correct procedures & materials.

Over the years ALR has learned of these procedures & has carried out many successful onsite repairs to machines that have succumbed to this type of grief. When we arrive onsite & discuss the repair times & costs involved for this type of front axle damage – we give an onsite repair option – which 99.9% of owners always take up.

Fact of the matter is that you don’t want your front axle to ever look like the picture below – so keep regularly greasing the king pins on your backhoe loader & if you raise the front wheels off the ground & notice any movement that should not be there – it’s best you address this ASAP – BEFORE things get real ugly!


The pictures below were taken of a 580SM after a regular customer had ceased trading & taken his machine to his rural property over 100km from ALR’s workshop. For quite some time I had mentioned that the king pins needed some attention ….. but you know how the story goes….

He had then dropped the machine in to his local repairer – which was a major agricultural dealer – to get a few things tidied up, to then sell the machine. Well, when the king pin slop was being looked at the only option was for them to fit a new or second hand axle under the machine, which was almost as much as the value of the entire machine. So the owner contacts me & pleads for mercy as he was aware that we have the ability to sort this kind of problem without handing over the family jewels. Both sides of the machine looked like this – it took two full days to repair including over 500kms travel – but the final repair bill was still streets ahead of what was being quoted & many thanks were given – as painful as that job was for this old school tradesman.


New bearing cup in a worn axle housing showing just how bad the axle housing can wear.

The above axle housing after some ALR onsite TLC


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