Swing cylinder rebuild

At work we have an old Kubota L2850 with a backhoe attachment made by Woods. When I first started working there,  the backhoe had its issues, such as slow swing movement from side to side, and a horrendous leak from the upper cylinder on the dipperstick. The upper cylinder was rebuilt about three weeks before this repair, so that took care of the leak there. The swing cylinder movement became worse, and eventually got to the point where unless you had the engine revved up really high, it would not move at all.  This is not good for the engine on the tractor nor is it good for the components of the backhoe that are still working ok.

When I examined the machine, I found that I could move the boom left and right by hand with almost no resistance.  Seeing as how there are check valves and so forth that make hydraulic components operate, this should not happen.  It was apparent that it is time for a cylinder rebuild.

What you need for this task:
-Hammer
-various large sockets
-torque wrench
-penetrating oil
-appropriate seal kit
-wrenches and ratchets
-floor jack (2 tons capacity or greater)

This is the bi-directional swing cylinder, meaning that it rides on the chrome shaft and uses a set of attached chains to pull itself to the left and right.  This is how the boom moves on the backhoe.  The first task is going to be removing the nuts that hold the chain to the actual boom. Seeing as this machine is older I soaked these in WD-40 first.

I am sorry for the poor picture quality here, but these are the nuts in question in the top photo.  Once these are removed, the chain is attached by a pin on the end of the cylinder body on the last link of the chain, as shown in the bottom picture.  A cotter pin is removed and then you can tap out the pin with a drift and hammer.  Remove the chain assembly and set it aside.

The chains should move somewhat freely, but these did not, so I soaked them in WD-40 and let them sit overnight.  Over time, they get caked up with dirt, dust, and other sorts of grime.  It also does not help that nobody on these "professional crews"  thinks to clean these machines off and grease them once in awhile.

 

 Just to the left of those hoses is a large bolt that holds the shaft in place.  You will have to move the stabilizer a little bit to access these bolts (one per side).  A floor jack will help with this task, if needed.

 





On the bottom is the impact wrench I tried to get the bolts out with.  On the top is my one inch impact wrench which I used because I wanted them out in a more timely fashion.  Sometimes I get tired of trying to make that half inch gun work, so when that happens I get out the big dog.

After removing the bolts from the shaft ends, and disconnecting the hoses that run into the cylinder body, I removed the swing cylinder with a little bit of effort.  I also set a drain pan under where the hoses are to catch oil coming out of them.  Finally I got the cylinder onto the bench and began disassembly, forgetting that there was oil in the cylinder still and making a huge mess in the process.



To disassemble the cylinder, remove the nuts at one end of the body and set aside, then remove the long bolts and set aside as well. Using a hammer, gently tap on one end of the cylinder body (you should be able to tell where it separates) until it comes out.  Remember that this is aluminum, and that it could crack, rendering it useless.  This is the time where you will want a catch pan for the oil that will come out all at once.  Or you can make a mess, like I did.

 

 

 

After tapping the other end of the body out, the shaft will come out with it. This white ring in the center of the shaft is the failure point.  Its job is to keep the oil from flowing all the way through the cylinder, creating two separate chambers that can be filled with oil and emptied of oil, which causes the movement of the cylinder.  In this case, the oil could fill the entire cylinder and move from side to side, which is why I could move the boom by hand.  This ring as shown is supposed to be one piece, not broken and worn.

 

 





 Open up your seal kit (in my case, Woods part number 37873) and make sure you have every seal in the package.  Using the operators manual, I took note of how many pieces were listed and placed them left and right side, and center.  The small "O" ring in the center is an extra part, so it is now in the spare parts bins, where it will probably stay forever.

In either end, you have a retaining seal on the outside and a wiper ring on the inside.  Pry out the wiper ring (blue hard rubber) and make note of its orientation.  It will be difficult to install the new one but I have found using a blunt tool to push the wiper into place helps.  Make sure to fully seat the wiper ring.  Using a pry tool, remove the retaining seal from its bore, again noting its orientation.  I have found using a socket that is about the same size as the seal and tapping it in with a hammer will seat it in the bore with minimal difficulty.  Also coating the new seals with clean hydraulic oil helps with installation as well. Do this on both ends.

On the inside of the cylinder end there are two "O" rings, one is round and one has flat sides.  Make note of where they go before removal and replace them in that same manner, again coating them with clean hydraulic oil to ease assembly. In this case, the flat sided "O" ring goes toward the outside, while the rounded one goes on towards the inside. These can be removed with a screwdriver but should be installed by hand.  They will stretch a little (a VERY little) and still retain their shape.

 

For some reason I do not have a picture of the center seals, but remove the remaining outer seal and the inner seal, again using a blunt instrument.  Again coat the new pieces in oil and reinstall. Like the "O" rings these will stretch a little bit and still retain their shape once installed.

 

Now you can reassemble the cylinder. After wiping down the shaft and making sure the cylinder body is free of old seal pieces or dirt on the inside, install one of the cylinder ends first onto the shaft, then onto the cylinder body tube.  This will take some effort so using a hammer and a large socket (one that fits over the shaft) drive the end into the body. Turn the cylinder over and drive in the other end.  Make note of where the hose connectors are, making sure one is on the top and the other on the bottom, opposite of each other.  Reinstall the long bolts and nuts, tightening them to 45 foot pounds of torque as mentioned in the service manual.  Reinstall the cylinder to the backhoe by first installing the bolts to the shaft ends, then connect the hoses.  You might have to move the cylinder position on the shaft to get it back in place and to line up the top and bottom hoses.  Lastly, reinstall the swing chains.  Make note of the holes in the link pins for cotter pin placement.  Test the machine and check for leaks.  If all went as it should have, there should be no leaks and smooth movement.