Case 580SM Travel mode unlocks on its own

[PeterJC]

My backhoe unlocks itself while driving but has also unlocked while sitting still. It’ll scare the pee out of you if you’re standing next to it. Have to treat it like a horse and not walk behind it.
The lock doesn’t appear to be worn.
When I lock it I make sure it’s completely engaged and then snug it in place. Am I doing something wrong?

Thanks in advance.

Peter

 

[Tinkerer]

Unlocks ??
What unlocks ?
Could you explain it a little better ?
What are you "snugging in place"?

 

[PeterJC]

Of course- The boom pops free from the lock.
For example: yesterday I was digging some holes for my neighbor. When I was done I brought the boom back, stepped on the lock mechanism and pulled the boom back and quickly pushed it forward into the travel position. Dropping the locking yoke onto the boom.
By snugging I mean that I pushed the boom forward, slightly, so that it was tight against the lock as opposed to being all the way back towards the cab with, maybe, a quarter inch between the lock and the boom.
I then started pushing some dirt around, a few minutes later there was a big yank backwards because the boom had popped free from the lock and locked position.
It did it again about ten minutes later.
I’ve had it happen a couple of times when the machine was just sitting there. It wasn’t even running.

Thanks

P

 

[Tinkerer]

Is there an electrically operated lock on the boom cylinder ?

 

[PeterJC]

No. Just the yoke which is lifted with a cable.

 

[Tinkerer]

Is there much wear on the yoke and or pin ?
Does the yoke drop completely down on the pin ?
No built up dirt around the bottom of the pin that would prevent the yoke from full engagement.
Do you think that welding a small extension on the pin would help ?

 

[PeterJC]

There doesn't seem to be any wear on the boom or the yoke.
I'll have to double check to see if there is any mud or junk under the yoke.
It really seems to lock in place. Just jumps out when it wants to. Could be bad if it happened at the wrong time.

 

[gggraham]

Make sure the latch rotates on the pin and the pin rotates freely, the latches had a bad habit of seizing on the pins. If the rubber stop in the boom is worn or not shimmed properly it can allow the boom to move back and forth too far this will jump the latch out as well. The boom should have very little movement back and forth when latched. It should be just enough to latch and unlatch. Seen many a boom bumper destroyed when the boom is slammed into place. That over center system is great if done properly.

 

[PeterJC]

Where is the rubber stop that you mention?
I don’t recall seeing one.

 

[PeterJC]

Here’s a picture of the yoke when latched.

 

[Willie B]

580K was a problem doing that. the facing surfaces get worn. I took the latch off & faced both surfaces to change the angle a bit.
There is a square bumper pad made from stacked tire material. If new & adjusted properly, it absorbs the impact of latching the boom. Also fills the slop in the latch.
It's called transport position, but I put the bucket on the trailer floor & chain it down. Also I don't latch it when roading at speed.

 

[Tinkerer]

Would replacing the rubber blocks (bumper) help ??
Latch Link

 

[gggraham]

The rubber block is located on the swing tower, it it is missing the boom slams back and forth and will unlatch. You can shim the one style. Like I said it should be tight enough to hold the boom but loose enough you can unlock without applying pressure to the block.

 

[Willie B]

These things will SLAM unless done by an expert. I use a stabilizer to push the bucket up. This makes latching gentle. First & second gear, latch the boom. Higher speed moving I don't latch it. I've replaced the rubber block on a few machines, they don't last very long exposed to petroleum leakage, or grease drool.

 

[PeterJC]

I don’t see the rubber bumper but I’ll look again. I considered travel mode to be whenever I’m not digging with the backhoe.
I drove up the hill to buy fuel and had to stop once in each direction to pull the boom back as I could see the yoke rising up and getting ready to pop loose.
When I parked I had the yoke in place (locked) and loose(I could wiggle it by hand). A day later it was tight. Seems like the boom wants to drop and when I’m driving around there’s enough movement that the yoke works it’s way up.
Oh, there is/was no dirt or junk built up.
Thanks for the ideas.

 

[PeterJC]

I don’t see the rubber bumper but I’ll look again. I considered travel mode to be whenever I’m not digging with the backhoe.
I drove up the hill to buy fuel and had to stop once in each direction to pull the boom back as I could see the yoke rising up and getting ready to pop loose.
When I parked I had the yoke in place (locked) and loose(I could wiggle it by hand). A day later it was tight. Seems like the boom wants to drop and when I’m driving around there’s enough movement that the yoke works it’s way up.
Oh, there is/was no dirt or junk built up.
Thanks for the ideas.

Bumper is there.

 

[Willie B]

My Super N is very slow as it droops, over three days it'll settle to where the bucket is on the ground. Motoring down the highway I unlatch, otherwise it'll bounce. Working the loader I usually latch it.

 

[Tinkerer]

Your rubber block is way past due for a new one.
In post #13 Gill said it is critical that has to be almost tight to the boom with a very small amount of clearance for the boom to move a tiny amount.

 

[Willie B]

I think the intent is it should be compressed when the boom is latched over center. Buffers the bang when you latch it & dampens the bounce when at speed. Older models had a shim set you could buy as the rubber mashed out. Those were made of 12? layers of tire cut to stack.

 

[gggraham]

We always shot for tight, not too tight not too loose. After 30 years at a dealer I can lift a boom and not slam at all. Takes practice to over centre the boom without a slam but it can be done.