3-Point Hitch Top link mount tore off back of differential case

[cdaigle430]

I wouldnt let Kubota off the hook completely here...yes 3 point mount BH are not recommended but...this looks like a bad cast to me. If you can proof it at least they will warranty the parts.

 

[California]

On the closeup pic, that rusted, tapped hole is concerning. Just speculating- not likely water could get down in there on a tightened bolt. Loose bolt would completely change the stress distribution on that assembly.

Good eye!

After reading that I went and looked again at the pic in Post 12. I see a polished dimple next to the left, remaining, vertical bolt. Could that indicate that the bolt attaching the 3-point upper bracket, was bottomed out which made stress that pushed the back of the transmission off? That might be a basis for a warranty claim.

 

[TMGT]

The more I look at the pictures the more I'm wondering what happened, low hr tractor, BH that doesn't even looked like it was used. If it had been used heavily/abused I could see damage, but this looks like it failed after mounting?

I cant see any casting issues from the pictures, and the rust on that through hole is common (the washer above it is a split washer).

 

[California]

low hr tractor, BH that doesn't even looked like it was used. ... this looks like it failed after mounting?

Paint on the bottom of the bucket and teeth is pristine, impossible if the bucket has ever been in the ground.

 

[TMGT]

Paint on the bottom of the bucket and teeth is pristine, impossible if the bucket has ever been in the ground.

Exactly, and that dimple you referenced is the bottom of the drilled hole for the horizontal bolt, doesn't appear to have had a bolt bottomed out in it.

I hope the OP can shed some light on what caused this, or at least the circumstances that led up to it.

 

[TMGT]

I actually just noticed something, there is a second pin in the top link bracket, with the larger solid top link of the BH I wonder if the BH top link bound on that second pin.

That could possibly put the full weight of the BH in a torsional load on the top link mount, which it is NOT designed to handle. One good bump and I could see it breaking if it didn't immediately. The way the casting is broken looks to support that type of loading.

 

[Henro]

I feel for the OP. What a bad situation!

But I am wondering what the manual for the tractor states regarding attaching a backhoe to it. I know with my B2910, it requires a heavy duty top link bracket if a 3PH backhoe is attached. Been using my 3PH backhoe for 18 years without an issue, But that is just me.

No doubt that a sub frame mounted backhoe is a better setup.

Do the manuals for more recent tractors than mine, which was purchased in 2002, prohibit use of a 3PH backhoe?

Curious more than anything...

 

[jmc]

The more I look at the pictures the more I'm wondering what happened, low hr tractor, BH that doesn't even looked like it was used. If it had been used heavily/abused I could see damage, but this looks like it failed after mounting?

I cant see any casting issues from the pictures, and the rust on that through hole is common (the washer above it is a split washer).

That's fair. I'd like to see the bolt/tapped hole on the other side though.

With a loose bolt, just the cantilevered weight of the bh driving down the road could reek havoc.

 

[TMGT]

That's fair. I'd like to see the bolt/tapped hole on the other side though.

With a loose bolt, just the cantilevered weight of the bh driving down the road could reek havoc.

Do you mean the bolt going straight down?

I've pulled the 3pt hat off a couple Kubota compacts and the through holes on the hat have always had some corrosion in them. Based on the corrosion on the 3pt balls etc. I'm guessing it lived outside for some of its life

 

[deezler]

I actually just noticed something, there is a second pin in the top link bracket, with the larger solid top link of the BH I wonder if the BH top link bound on that second pin.

That could possibly put the full weight of the BH in a torsional load on the top link mount, which it is NOT designed to handle. One good bump and I could see it breaking if it didn't immediately. The way the casting is broken looks to support that type of loading.

This is an intelligent hypothesis. A picture of the bottom of that backhoe's top link could show if the paint was rubbed where it would have contact the second, lower top-link pin that was left in the mount there.

 

[deezler]

That's fair. I'd like to see the bolt/tapped hole on the other side though.

With a loose bolt, just the cantilevered weight of the bh driving down the road could reek havoc.

Eh, I think even one day outside in the rain after the failure could rust up those bolt hole threads. Note the bucket placed over the steering wheel and dashboard for rain protection.

 

[clemsonfor]

Do you mean the bolt going straight down?

I've pulled the 3pt hat off a couple Kubota compacts and the through holes on the hat have always had some corrosion in them. Based on the corrosion on the 3pt balls etc. I'm guessing it lived outside for some of its life

With that wheel barrow tub over the operator controls I would say it's probably outside or it's shed kept and when it broke he put the tub on it to protect it untill it was moved? I would cover the open transmission area too but that if it was covered has been removed for a clear pic.

 

[jmc]

Do you mean the bolt going straight down?

I've pulled the 3pt hat off a couple Kubota compacts and the through holes on the hat have always had some corrosion in them. Based on the corrosion on the 3pt balls etc. I'm guessing it lived outside for some of its life

In the closeup on post #1, I'd like to see the bolt at the 7 o'clock position from the filler cap.

My thought on the rusted bolt hole was that on a really tight bolt, it would be hard for water to wick between the compressed, mating flanks of the 60 degree thread forms. Maybe on the non-compressed flanks though. That rust looks very scaly.

As far as that rust occurring after the accident, the adjacent broken casting is pristine.

 

[TMGT]

Eh, I think even one day outside in the rain after the failure could rust up those bolt hole threads. Note the bucket placed over the steering wheel and dashboard for rain protection.

Yup, even the time it spent on the dealers lot can cause that corrosion. The threaded area thats visible isn't rusted, only the through bolt hole.

 

[TMGT]

In the closeup on post #1, I'd like to see the bolt at the 7 o'clock position from the filler cap.

My thought on the rusted bolt hole was that on a really tight bolt, it would be hard for water to wick between the compressed, mating flanks of the 60 degree thread forms. Maybe on the non-compressed flanks though. That rust looks very scaly.

As far as that rust occurring after the accident, the adjacent broken casting is pristine.

I dont think any of that rust in the bolt hole happened after the break, non of the threaded areas visible have rust, just the through hole.

 

[California]

I actually just noticed something, there is a second pin in the top link bracket, with the larger solid top link of the BH I wonder if the BH top link bound on that second pin.

That could possibly put the full weight of the BH in a torsional load on the top link mount, which it is NOT designed to handle. One good bump and I could see it breaking if it didn't immediately. The way the casting is broken looks to support that type of loading.

I think you're on to something there. The top link has a visible shoulder, where the solid bar is welded to its rounded end. If there is the same shoulder on its underside, that lower shoulder could have jammed against the lower pin and not let the hoe go any lower. So instead of the 3-point arms supporting the hoe, that unintended contact carried all the weight. Then drive out to the worksite with that jammed surface carrying the weight of the hoe and lurch over a bump - and you have the forces to break something.

 

[ptsg]

I think you're on to something there. The top link has a visible shoulder, where the solid bar is welded to its rounded end. If there is the same shoulder on its underside, that lower shoulder could have jammed against the lower pin and not let the hoe go any lower. So instead of the 3-point arms supporting the hoe, that unintended contact carried all the weight. Then drive out to the worksite with that jammed surface carrying the weight of the hoe and lurch over a bump - and you have the forces to break something.

It does make sense. There is no lateral play on the that rigid top link. Along with the natural play of the lift arms, it allowed it to twist the top link mount like you said.

But in all honesty, that's an awful thin casting for all the stresses it has to handle. Even just roading the tractor and hitting a bump or something with a slightly heavier implement in the back, can possible cause damage to that.

 

[the old grind]

For all we know OP didn't get to dig much with this and cracks might have begun just while driving with that much overhanging load. I'd sell the BH to pay for repair if I had to.

As a 20ph Terramite owner I kinda cringe when seeing smaller BHs on 40 hp machines that weigh 1 1/2 times as much. My T5C says 8' 6" depth and I've done 5'+ with ease trenching in for barn hydrants. Whole thing weighs < 3k lbs wet and will drive (snugly) through a 4' gate. btw, doesn't mean it won't stall leaning into big roots or rocks, and a ripper tooth is accessory-1 for many of us who are seriously digging vs dabbling.

Point is to support that BHs & bits made to do the work don't break. As for mounting one on a SSQA plate, what this did to the 3PH says I wouldn't want all that weight/load on my loader arms and I'd happily trade my skid-steer for a bigger Terramite. It's a bit late to suggest a boom & bucket SSQA option, and not all if us have a skidder.

btw, when one of our guys in OH lost an engine and had to spring out of pocket for a short-block he struggled to find at all I mentioned a crowd-fund. The idea fell flat, but I'm glad to hear that the spirit lives on. If we can't go back in time let's go forward.

 

[Rustyiron]

It does make sense. There is no lateral play on the that rigid top link. Along with the natural play of the lift arms, it allowed it to twist the top link mount like you said.

If I understand this post mortem (2 pins in top link hole(s) caused a fulcrum/rotational situation) correctly, the top link on a 3pt BH is not functional like on any other attachment. There's a "stiffleg" that go's from the lower lift pins to the top link. Without this you would be unable to put the tractors weight down to the outriggers and would be relying on the BH weight ONLY to do all the digging, or it's no longer a parallel arms movement (lift arms and top link) as in a normal 3ph. You can see it in the first picture.

 

[Sawyer Rob]

Wondering if anyone has experienced (prefer first hand; happened to your tractor) a top link mount being torn off the case of your tractor (any model or make).

I saw a L series Kubota one time that the top link tore open the case, even more than yours.

He had made a 3 point skidding attachment to pull logs out of the woods with and had a chain from it, to a bigger log. While pulling the log he heard a POP and it tore the azz of the tractor open.

My guess is, it cracked over time earlier, and got finished off that day... That's why I like the heavier/stronger castings of a farm tractor, a skidding winch would have helped him too.

You keep pulling on those thin castings, and sooner or later, something is going to give!

SR