Adding zerk/grease fitting?

   / Adding zerk/grease fitting? #1  

Jason280

Bronze Member
Joined
Apr 17, 2012
Messages
89
Location
Ga
Tractor
Kubota L4330
I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.
 
   / Adding zerk/grease fitting? #3  
I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.
This sounds like a good fix.
 
   / Adding zerk/grease fitting? #4  
I would imagine this is just fine, if it's the same side that always breaks I'd wonder about the alignment of the FEL/arms/cylinder though.
 
   / Adding zerk/grease fitting? #5  
No reason your idea won’t work. Some bushings have grease grooves. My old M5030 had both grease points with protection collars on those very pins.

Broke a lower ssqa pin similar pin on the M59. Previous owner not friends with a grease gun. Replaced the four pins and may at some point replace the bushings. Surprisingly inexpensive. Old pins showed wear on one side probably flexing under load.

Any grease is better than no grease. Moly grease is preferable for these large pin/bushing joints.
 
   / Adding zerk/grease fitting?
  • Thread Starter
#6  
I would imagine this is just fine, if it's the same side that always breaks I'd wonder about the alignment of the FEL/arms/cylinder though.

At least once its been on the opposite side, where the rod is for bucket position. The pins are exactly the same, with the exception of the additional "boss" for the bucket rod assbly to attach.
 
   / Adding zerk/grease fitting? #7  
just a little aside.... are you using Kubota OEM pins or aftermarket?

i was told by my local parts supplier that their is so much junk / poor quality stuff flooding the market for some time which probably includes soft / weak pins. He says he regularly de-lists certain suppliers only to find the next in line banging on his door to buy parts flogs him the same inferior stuff. He called it a race to the bottom of quality. Price seems to drive a lot of buyers decisions. He claims it is getting very hard to find high quality / easy to find inexpensive sh@t.
 
   / Adding zerk/grease fitting? #8  
I have an '03 L48 backhoe, with roughly 1100 hours. I've now broken the hinge pin on the FEL 3 or 4 times (I think its called "Pin 7"), the pin that attaches the ram end of the cylinder to the tilt portion of the bucket attachment. This pin has a grease fitting on the end, with a hole drilled through the middle to a center portion groove. The groove has holes, where the grease expands out to lube the pivot. The pin has always broken at this groove. On my much newer 7060, the same pin has no groove, and no grease fitting....instead, the pivot is lubed by an external zerk that is threaded through the end of the cylinder ram (on top). This means the pin is a solid piece, with no extra holes or grooves (to potentiate fractures).

Here's my question. Any reason I can't simply use the newer style pin, and drill/tap the ram end on the L48 cylinder for a zerk fitting? This is how the 7060 is set up, and the pins are the exact same diameter and width. I do understand this leaves the zerk a little more exposed, but I could always tack weld a small collar around it for protection.
Sure, you can put anything in there that you want. I know that some pins break, and it is just a simple enough of a problem to be interesting to us simple kinds of guys.

What do you think? Have you put any time into seeing why it broke? Photos? A rounded groove is not much of a crack potentiator. As you describe it, it almost sounds like there is more friction on one side of the center groove than the other. That would give it a twisting force to break the pin at the center instead of a shearing force out at the end.

Any chance that the pin is somehow constrained on one side and not the other? That could happen if the the grease goes to one side and not the other? Or maybe different types of grease were used? grease incompatibility is real, and gives you a hardened clay "dam" that blocks grease flow.

I've also saw here on TBN a few years back a complete Kubota technical design foul-up where the pivot pin was fastened against rotation at one end ..... actually bolted to the loader arm.

I ask all these questions because I've found that grease and pivot failures are likely to happen again unless the cause is cured.

I'll see if I can find a diagram. Most pins are free to rotate and are mounted in double shear....which makes it even less likely for it to simply shear and more likely that it is a torsional failure. If that is what is happening, you should probably mount TWO ZERKS at the 1/3 points instead of one at the center. Allow it to rotate - it's hard to beat a free floating pivot pin with a couple of washers and a cotter pin or two keeping it in place. Use a grease with a wide compatibility base chemistry. JD's green modern polyurea type is one of the better ones. There are others. I don't use moly because of the mess. YMMV.

BTW, just to complicate a simple job, ZORO.COM has a great selection of zerks. I went crazy and bought this zerk thread gauge. Do yourself a favor and stick with something simple like NPT....

rScotty

Screenshot 2023-03-08 at 1.34.48 PM.pngScreenshot 2023-03-08 at 1.38.15 PM.png
 
   / Adding zerk/grease fitting?
  • Thread Starter
#9  
Oddly enough, I have three different Kubotas with FEL's, and it's the only one to ever break a pivot pin. That being said, my old '07 4330 (if I remember correctly, it's been replaced with a MX5400) and newer 7060 both have the external zerk fittings on the pins.
 
   / Adding zerk/grease fitting? #10  
Right. It seems like in every mechanical device there is more than one way to do it. When looking at wear or failure it's interesting to see if there is some simple & better way to make it.

Pivot pins are an example how a little thought can make a big difference. After all, if a designer can't make a pivot pin that lasts, it's probably worth taking a hard look at the rest of the loader.

I will say that the loader on our M59 is well thought out in every detail. I don't know if other Kubota loaders are the same or not.

rScotty
 
 
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