L35 - BT900 Backhoe Swing Overhaul

PoTreeBoy

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So as not to clutter @Nicksacco's thread any more, I decided to start my own. Excuse the repetition. My thread is not nearly as complete as his, but may have a few nuggets. For one thing, mine has gone much smoother than his so anyone contemplating this job shouldn't start out too pessimistic. So smooth, in fact, I'm waiting for the pending disaster to hit.

This is about the swing section only. My tractor has had a lot of play in the swing since I've owned it, so this job has been in the queue. One of the cylinders blew a seal last week, so I took that as the sign that the time was right. (I think I could have repaired the cylinder without removing it.)

First, I dismounted the backhoe. It might be possible to do this work with it on the tractor, but having it out of the way is nice. Besides, I'd wanted to know how to do it. The only problem was getting the handles that control the top jaw locks freed up. Mine were relatively easy, I did remove the wheels for access.

Once the handles were free, removing the backhoe was by the book, easy. I did leave it elevated on the stabilizers with jackstands under the lower attachment pins. Then remove the cylinder rod pins. The pins looked surprisingly good, but the bushings show obvious wear. The pins can be easily replaced in the future, so I've decided to keep what I have. At this point I decided to replace hoses and bushings, and refurbish the cylinder trunnions as well as repair the seals.

Next, I should have removed the back panel for valve access and the operator console from the main frame. Instead, I started working with them in place. I should have marked and removed the hoses first, but instead I removed the top support plate. Without the hoses in there the plate might come out differently, but I slid it out the side over the stabilizer. To clear, the stabilizer cylinder has to be horizontal, so I had to hook the hydraulics back up and let the jack stands hold the hoe up temporarily.

So, remove the rod pins, rock the console back for access, mark and remove the hoses, remove the top support plate, then remove the cylinders.

I measured and ordered the six hoses, about $230. Today, I took the cylinders to have the seals replaced. I asked the man to leave the glands loose, since I anticipate welding on the cylinders and don't want to overheat the rubber parts. On the way back, I stopped by the Kubota dealer and ordered the six bushings, about $100.

Then started the search for a machine shop to weld and machine the trunnions. First shop, yeah we could do it but we're swamped. How about x, close by? They don't do repair work. After a few more calls I think a guy a couple of miles away from the cylinder shop is going to go by tomorrow to look at them to make sure he can do it. If so, he can pick them up, saving me a 30 mile round trip. If that fails, I think I have a backup shop.

Back home, I decided to tackle the bushings. After all the cut, grind, torch, etc. stories, I was dreading this. As a warm-up, I found a socket to use as a mandrel and took the top support to my nephew's 15 ton press. Pressed those babies right out, easy peasy! OK, what about the bottom ones? They're trickier since they're in the main frame, so can't take them to the press. And, there's a thin ring welded in the bottom of the bore to form a shoulder, preventing the bushings from coming out the bottom. Maybe I can pull them out. My lucky day, the socket/mandrel was small enough to slide in the stop ring, but large enough to drive the bushing. So I rigged a draw setup, shown below. That's a Gr 8 3/4" NC bolt through a socket on top large enough to clear the bushing, then through the bushing, then the mandrel/socket. Grease the nut for good measure. Put the 1" drive breaker bar with cheater to it and, amazingly, it pulled out. The only casualty was the bridge of my nose when the 1-1/8 backup wrench fell off. Fortunately, my glasses were ok.

1000006611.jpg

Here's a picture of the 4 trunnion bushings, top 2 on top don't show as much wear as the bottom ones. It was definitely time to replace.
1000006616.jpg

You can see there's a groove in the outside, so it's not absolutely necessary to line up the grease hole with the zerk. There was grit in that groove, so it had to work its way through the bushing bore and out through the grease hole. As @Nicksacco has mentioned, the bottom of those bushings is open, so dirt can get right in. I plan on making some shields to cover them, leaving a small hole so grease can flush out.

Tomorrow, actually later today now, I have some coordination to do and, if all goes well, I should have cylinders ready to go no later than early next week.
 
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Nicksacco

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Kubota L35 TLB, 2014 RTV-1140CPX
Sep 15, 2021
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Nice job my friend!
I think your advantage is that your tractor doesn't appear to have been at the bottom of a lake!
I swear mine was with all the rust it had.

What are you thinking regarding the trunnions?

a) cut them off and weld on new ones
b) shave them down and weld on like a pipe that would fit the bushings
c) ??
 

PoTreeBoy

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Nice job my friend!
I think your advantage is that your tractor doesn't appear to have been at the bottom of a lake!
I swear mine was with all the rust it had.

What are you thinking regarding the trunnions?

a) cut them off and weld on new ones
b) shave them down and weld on like a pipe that would fit the bushings
c) ??
Wait, your tractor, loader and backhoe were submerged? I thought maybe it was exposed to salt.

The plan is to weld the worn metal, then machine the trunnion back to original size.
 

Nicksacco

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Kubota L35 TLB, 2014 RTV-1140CPX
Sep 15, 2021
747
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Bahama, NC
I honestly don't know what kinds of abuse my machine went through to have so much rust on it.
But those days are finally over.

And as for OSPHO, I would recommend it for ease of use - but too early to tell if any further rusting will occur. I'll likely report on that next year.

The most I could get out of Kubota USA was that it was purchased a long time ago in Western NC from a dealer that no longer exists.

I hope you post pics of the swing cylinders once the machining has been completed.
 

PoTreeBoy

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Nice job my friend!
I think your advantage is that your tractor doesn't appear to have been at the bottom of a lake!
I swear mine was with all the rust it had.

What are you thinking regarding the trunnions?

a) cut them off and weld on new ones
b) shave them down and weld on like a pipe that would fit the bushings
c) ??
The plan is to have them welded up and turned back down to new tolerance. I have new bushings on order.

The machine shop nearest my second home was swamped, so he referred me to a shop near the hydraulic shop. That made it convenient to make the parts transfer. The referrer had hired one of the referee's employees, that's how he had the contact. The referee mentioned that when I talked to him, hope he doesn't hold it against me!

I feel so ignorant. I was thinking the best way to machine those trunnions, assuming you didn't have a big enough lathe to swing them, would be in a mill with an external boring bar. I think he's planning on doing it with CNC. I guess with 4 or 5 axis CNC you can mill a round part, internal or external, with a standard mill bit?

He first tried to talk me out of doing it, he didn't think the wear is that bad. But it has pits and scores from the grit. I've gone this far, I'm going first class. Or at least coach, edit: I meant business).
 
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PoTreeBoy

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Just picked up my cylinders at the machine shop. They're a lot better but certainly not new. He mentioned having a problem with tool chatter. He attributed it to the thin cylinder thickness, but I'm not so sure. He set a chuck on the bed and clamped the lower trunnion in it while machining the top one, so the thin part of the cylinder wasn't in play. Once I get the bushings I may polish it a little. I'm more concerned with one small area where he didn't overlay enough. I'll just grind a little so the edge doesn't dig into the bushing.
 

Nicksacco

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Kubota L35 TLB, 2014 RTV-1140CPX
Sep 15, 2021
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Sounds good.
Maybe the chatter was because of the way he mounted the cylinder for miiling. Could be the tool was extended far enough to vibrate.

Heck, at least your getting a long needed repair done as good as possible.

So were the trunnions welded, then turned down? The welds would be a lot harder than the oem material. Could have something to do with it.
 
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PoTreeBoy

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Sounds good.
Maybe the chatter was because of the way he mounted the cylinder for miiling. Could be the tool was extended far enough to vibrate.

Heck, at least your getting a long needed repair done as good as possible.

So were the trunnions welded, then turned down? The welds would be a lot harder than the oem material. Could have something to do with it.
Yes, he welded them. I think he's a better machinist than welder. I don't know what process he used. As long as they fit the bushings when I get them, I'm satisfied.
 

PoTreeBoy

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Cut out some 'dust' shields to cover the lower trunnions. Will finish tapping the holes when the new taps arrive.

1000006650.jpg
 
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PoTreeBoy

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Having received the back ordered spiral wrap in Tennessee yesterday, I drove to Mississippi today. Picked up the bushings at the Kubota dealer and tried them for size. Then I pressed the two in the rod ends and the two in the top support. The last two will have to be pulled in the frame.

Noticed something interesting. The two rod end bushing packages said 'Made in USA' with nothing on the bushings to indicate otherwise. However, the trunnion bushing package said
1000006691.jpg

but inside said
1000006692.jpg

Can Kubota not keep up with their supply chain?
 
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PoTreeBoy

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Today I pulled in the last two bushings, installed the cylinders and top support.
For @Nicksacco I'm including a picture of the repair job, this is the worst area. I smoothed it a little with a small grinder.
1000006693.jpg

Notice: I had to remove the top support and press one bushing a little to get the plate down enough to get the bolts in. I didn't realize there is so little clearance in this area. Also, you need to make sure the bottom bushings are drawn up to the stop.

I started putting hoses on when I realized the 90deg ends have a longer tangent than the originals. It looks like this could hit the frame on the two crossover hoses. If I can't get a shorter 90, I'm going to use a male x female swivel 90 fitting and put straight fittings on the hoses.
 

Nicksacco

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Kubota L35 TLB, 2014 RTV-1140CPX
Sep 15, 2021
747
477
63
Bahama, NC
Good 'ole rust eh?
Nice job on those!

Something to consider depending upon what hose size you have on the swing cylinders is a large tie wrap.
I used the kind for HVAC and fastened the hose to the cylinder to keep the hose fittings from getting loose due to the back and forth motion.

I needed new hoses and really wasn't sure what was already there - and what the proper length would be. With Messick's help, we located possibly the last ones in the USA!

So if you need cylinder hoses, I can tell you the OEM lengths.

These are the hoses I added the tie-wraps to:

1761720168931.png