# Need help with a IH 3121 backhoe attachment.



## Lester Herrington (Sep 11, 2017)

I have a IH 2504 Industrial tractor with a IH 3121 backhoe. From what I was told, a falling tree struck the side of the unit and the force broke the piston assembly that moves the unit left/right. The 6 bolts holding it and the right side ejected from the assembly but I cannot see anything that looks broken inside. I bought the parts manual, but the images of this unit are so poor that I can see little to no detail regarding how it works but from what I can tell, the piston has teeth in it that engage a half moon gear creating the movement.

I am assuming that moving the boom all the way to the left, I should be able to re-insert the assembly and feed it in while I move the boom to the right. I would love some insight from someone who has more experience with this.


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## marc_hanna (Apr 10, 2017)

From the looks of it you will need to disassemble it enough to clean up those bores and install a new o-ring. That gearbox will need to be filled with oil. While it's apart you can connect the cylinder to your tractor and make sure it still actuates properly or if the seals or whole cylinder need to be replaced.

I'm not sure, but it looks like some of the bolts were snapped off. You may need to drill and re-tap.


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## Lester Herrington (Sep 11, 2017)

Yeah, everything will need to come apart and get cleaned and lubricated. I am finding plenty of sources for parts for my tractor but am not coming up with parts for the hoe. Is there such a thing as a rebuild kit for these components? There looks to be a rubber O-ring and a metal ring that much expand against the wall of the cylinder.

The bolts fortunately are coming out easily, I was able to remove 4 of them with just vice grips, the other two should come with a little lubricant and elbow grease.

I am wondering if there is a trick to getting the piston back into the cylinder. My thought is to run a chain from the top of the backhoe arm to the bucket so that I could swing the arm back and forth. It seems if I swing it all the way to the left, that I could start feeding it in while I slowly move it to the right. I don't want to re-invent the wheel if there is a better way to do this. I am dealing with a great deal of weight...


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## marc_hanna (Apr 10, 2017)

I would think that after you have it all cleaned up and with the hydraulic lines disconnected, it should slide in relatively easy. You could use a couple ratchet straps and hang it from your FEL to take some of the weight off when you're trying to align it.

I think the seals, o-rings, and bolts are all standard shelf items. If the rod is too pitted such that it won't maintain a seal, you may need to get it chromed and reground. I assume that would likely be the most expensive aspect of the whole ordeal. If you can't find the size and tolerance specs, you could contact a mechanical engineer and they'd be able to tell you.


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## RC Wells (Dec 26, 2008)

Are you referring to the swing rack as a piston? The component with the broken bolts.

If so, you remove the gearmotor, unhook the hydraulic line on the other side so that one will turn as you swivel the boom. Then reinstall the motor you removed, reconnect the hydraulic lines and you should be good to go.


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## marc_hanna (Apr 10, 2017)

RC Wells said:


> Are you referring to the swing rack as a piston? The component with the broken bolts.
> 
> If so, you remove the gearmotor, unhook the hydraulic line on the other side so that one will turn as you swivel the boom. Then reinstall the motor you removed, reconnect the hydraulic lines and you should be good to go.


Okay, I see what the OP is asking now. He's trying to figure out how to walk the rack back into the assembly. Sorry, I thought he was trying to compress the cylinder back in.


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## marc_hanna (Apr 10, 2017)

There might be a removable lynch pin on that pinion so that you can rotate it independently of the arm.


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## RC Wells (Dec 26, 2008)

Once the unit with the rack is disconnected and the hydraulic lines from both sides are removed, it is not necessary to swing the boom to install the cylinder as long as the big pivot pin is not broken. Take the cylinder with the rack that has the broken bolts off and make sure it is free to move. Extend the rack to its centered position (assuming the boom is centered), then twist the cylinder 180 degrees so the its rack clears the rotational internal gear set, drop the rack down to clear the internal gear (half moon) then twist it and lift the rack to engage the teeth, think key in a lock). bolt it just snugly until you have verified the swing range.

It can get a bit tricky here as if the boom is not centered, or the rack is off a tooth, the boom will not be able to fully swing from side to side. It also requires the cylinder on the other side to freely move as you check the swing. Oil will squirt out of disconnected cylinders as you check the range of swing motion.

Once the racks are engaged, and the boom swings freely in a full range of motion from side to side the hydraulic lines are reconnected and the bolts torqued. Should be ready to test with hydraulic pressure.

I should mention that 9 times out of 10 it is necessary to rebuild both cylinders if the hoe has been idle for an extended period. This is necessary to assore the cylinders move easily during the installation process.


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## Lester Herrington (Sep 11, 2017)

Hi all, when I finally got around to it, I was able to weld the metal piston case and found that the o-rings were standard items that I was able to purchase online. As recommended above, I was able to lube up the piston and it slid on enough to start a few bolts and draw it in the rest of the way.

Everything seems to be working well, thank you for your comments and suggestions.


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