Steering knuckle failure

[gwdixon]

The guy I sold my L3650 to 4 months ago called today to say the right front steering knuckle had snapped off where rod attaches to the housing.

In looking at it, there was a clean break where the bolt on the rod attaches to the hub. It will cost $1200 to fix. I don't recall hitting the tire or wheel with anything that would remotely cause such a failure.

Did a search and came up with nothing about this problem. The early Hummers from GM had this same type of problem and were recalled if I remember correctly. Anybody know anything about this issue in a Kubota?

I'll try to get some photos if anyone is interested. Thanks for any information or insights.

 

[jlrsn]

A person had her Kubota Front Axle Casting Break while mowing: Complete different machines but.....:

(http://******************.com/kubota/1959-kubota-manufacturing-plants.html)

Substitute "machine-under-ground" without the dashes for the ********* above and right after "kubota" replace "manufacturing-" for the "ing". TractorByNet does not allow the competition to be posted

Good luck,
Jim

 

[jlrsn]

A person had her Kubota Front Axle Casting Break while mowing. I'll send you the URL as a PM as every time I try to put the URL in it gets unreadable by TractorByNet
Good luck,
Jim

 

[gwdixon]

Thanks jlrsn.

Attached are photos of the problem. It appears that the force would have had to come from above or below to snap off the attachment point.

 

[dfkrug]

Wow, GW, that's quite a failure. Thx for posting.

The good news is the tractor is old enough to make finding a used part
at least possible. If I were the owner, I would find out what other tractors
use the same part, too.

There is also little risk to trying to grind some serious chamfers and welding.

Also, those MFWD hubs are not hard to take apart.

 

[SockPuppet]

My first post here!

It looks like the piece was already cracked from the pics and I'm going to guess the tie rod end was over-tightened and wedged the first crack in.

 

[ultrarunner]

I once got wedged pointed downhill between two trees... no matter what I tried, the front tires just deformed and wedged tighter... my first thought is something is going to give and it won't be the trees.

Ended up using some chain and a chain fall to extricate myself...

 

[Adiredneck]

My neighbor had the same break a couple of years ago with his 1992 L3450. He figures there must have been a pebble or something that got wedged into the knuckle & cracked it. Part of the break was rusty, and part was not, so it had been like that for a while.

He unbolted the housing, took it to a machine shop and they welded it for him. The machinist mentioned that there was a high nickel content in the cast and it welded easy. It was a cheap fix for him and he uses his tractor almost every day.

 

[gwdixon]

Thanks for all of the replies and suggestions. Your collective wisdom will be forwarded to the owner.

Grinding a chamfer and doing a 100% weld on that casting would be quite a feat - far beyond my skills but it is nice to know of the possibility of having a machine shop or welding shop do it.

The pictures show a slight discoloration on the upper portion where the tapered bolt goes through the casting. Maybe it was an existing condition or had been cracked for some time. There is no rust in the discoloration however. (The surface rust on the fresh break is from an overnight rain.)

The owner had it hauled to the local Kubota dealer today for a brand new casting. I called and asked him to have them save the old parts. It will likely never break again but it might be interesting to try a "farmer repair" on it just for practice. The taper could probably be re-machined by a machine shop.

 

[Adiredneck]

GWDIXON:

$$That's gonna hurt! Cast is not something I am capable of welding either. My father broke a cast pulley last year on an old IH 300 Utility. He removed it and a friend vee'd out the edges, clamped the pieces together, heated them and did a darn good job reairing it. It's working good. He also welded a broken ATV axle for me a couple of years ago. He welded a little bit, then walked away for a 1/2 hour, then another pass, repeat... Came out good and true.

Too bad your friend couldn't have tried to do a repair first, before paying to have it all replaced. There's not much to taking it apart to bring to a machinist.

I like the picture in your Avatar.

 

[PILOON]

While I am not an expert, but from experience I'd say that is a fresh break caused by serious stresses like wheel jammed between 2 rocks and forcing with power steering or some such forces, or hitting a curb while turning etc.

An old break or crack would have much more tell tale rust and also maybe some chatter or polished faces in crack area. I don't detect any from your pics.

For sure you are not responsible in my opinion.

 

[nh DRAGON]

While I am not an expert, but from experience I'd say that is a fresh break caused by serious stresses like wheel jammed between 2 rocks and forcing with power steering or some such forces, or hitting a curb while turning etc.

An old break or crack would have much more tell tale rust and also maybe some chatter or polished faces in crack area. I don't detect any from your pics.

For sure you are not responsible in my opinion.

Agreed, We all feel terrible when this type of thing happens but it does.
And no matter whether he was forcing it to see what it would do or just cruising the back nine, Still a fresh break and not your fault!

 

[Chilly807]

We see this kind of thing at work quite often, although it's more often rotating machinery in our case.

In my opinion, the upper portion of the taper wasn't in contact with the stud for quite a while, maybe from new. It was probably not a good angular match from the get-go.

The presence of old rust in that area means there was no contact metal-to-metal. A tapered fit requires 80-90 % contact for good working strength.

The only part of the hole that was providing support to the stud was the bottom 30%. When the housing finally broke, the stud was tough enough that the cast housing broke first, for the stud to break it would have had to pull apart which is unlikely in this application.

The darker area at the upper part of the knuckle may have been the beginning of the crack for a few months, it's hard to tell without metal analysis.

Great photo George ! We have techs at work that do only that and we often don't get such good quality !

Chilly

 

[gwdixon]

Chilly807: Thanks for taking the time to do such a detailed anaylsis. Your reply and the others on this thread is what makes TBN such a wonderfully helpful site.

I'd apply for a photography job at your work but Nova Scotia is a little too severe for us California wimps!

 

[taborekle]

Am I the only one that things that $1200 for a small tappered casting is outrageous. Wow.

 

[RickB]

Am I the only one that things that $1200 for a small tappered casting is outrageous. Wow.

It's the entire swivel housing less the hub cover and internals. Still plenty costly.

 

[Chilly807]

I suspect that is the out-the-door price, labour and taxes, etc. Still plenty expensive, I'd be pale for a couple days after that kind of bleeding..

You're welcome George, figuring out why things break is part of the fun of my job... You'd get used to the cold after a couple days, I hardly even notice anymore til it's -20C !

Chilly

 

[dfkrug]

The owner had it hauled to the local Kubota dealer today for a brand new casting.

Oh, too bad. A burnt L3350DT just came up on CraigsList yesterday in
San Jose.

 

[gwdixon]

Oh, too bad. A burnt L3350DT just came up on CraigsList yesterday in
San Jose.

I saw that burned L3350. How pitifully ugly. What a shame. Below is a low-res picture.

RickB is correct. The parts manual shows that the whole housing is cast in one unit including the attachment point.

The casting alone was $650. The replacement price OTD was negotiated down to $1100 for everything but now, since the thing is apart, the gaskets and seals will be replaced so it will come in just under $1300. Hope the dealer isn't pulling a fast one for a few bucks. However, I'd probably have the gaskets and seals done voluntarily if the tractor was still mine.

Oh, and my first name is Gary but you can call me George if you want.

 

[Willl]

Your not footing the bill for this are you ?