580B Broken tooth on Spur gear

Hello All,
Its been a bit since I posted last, but I read through this section quite often and I'm hoping someone here has some experience that could help me. Since i acquired my 580b its had an intermittent rotational tick in the rear end. It is most noticeable when moving at faster speeds and rarely is heard when moving slowly. When changing out the shuttle fluid and draining what looked like yellowish puke from the rear diff I went looking for a way to clean out the gunk from the rear end. After pulling off the rear access/pto cover i noticed something stuck in the sludge in the bottom of the case. I was hoping it was a wayward leaf or similar, but when a handheld magnet dragged out a single broken off gear tooth I knew I was in trouble.
At first I couldn't figure out where it came from, but after narrowing down by shape and size, then getting an inspection mirror at just the right angle while a friend slowly rotated the wheels, I saw that it had relatively cleanly sheared off of what seems to be referred to as one of the spur gears. Its one of the smaller straight cut gears that directly drive the 2 big final drive gears on either side of the case.
Question is, has anyone else had this happen or maybe can speculate as to what would cause this? after looking up the part it seems like that side is tied into the diff lock function possibly. Also, is this repairable without splitting the tractor? it seems like there is a removable side cover that hold this gears shaft in place....
Any info and relevant experience would be very helpful as a family friend suggested that the best option might be to simply fill it back up with gear oil and try not to strain it too much...

They call that a Pinion gear. And yes access is thru the side cover once get all the other stuff out of the way like the Tire and wheel.

we call the big gear the bull gear and the small one the bull pinion

anyone have experience doing a replacement of this gear? opinions on what causes a failure like this? would anyone put off a repair like this if the machine was only used lightly?

Shock Loaded, Wheel spinning and caught Hard.

If all it is doing is knocking, it's not jumping or slipping and catching, I have seen things run the rest of their life with one gear tooth missing.

any time a gear tooth is missing, it overloads the next tooth and could cause another one to break or jam. i personally would just fix it, if the parts are reasonably priced and time allows- then it will not fail later at an inconvenient time or place and before it damages the bull gear. just my 2 cents

Call me a pessimist,...... I tend to agree with @56wrench
Sorry @mitch504

Fix it. There is plenty of great help and experience here........just make sure we aren't drunk-posting repair advise LOL

alrman said:

Call me a pessimist,...... I tend to agree with @56wrench
Sorry @mitch504

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Welllllll, if it was mine, I'd fix it, cause I agree with 56wrench, too.

But, I have seen a lot of stuff run a long time with one tooth missing. If this is a homeowner machine, or something that is going to run 4 hrs a month burying conduit, and they take my advice, it'll jam tight in the highway in twenty minutes. If we hadn't discussed it, it'd go 20 years.

XcessReality ... Are you a betting person? Consider yourself as betting against the house. When another tooth breaks, the odds are the machine will be working far from the shop. Will the broken tooth fall harmlessly to the bottom of the gear case? Will the bull gear survive the broken gear or like many gears sets transfer damage? Folks do win the lottery against the odds. But the odds are against them and you.

hosspuller said:

XcessReality ... Are you a betting person? Consider yourself as betting against the house. When another tooth breaks, the odds are the machine will be working far from the shop. Will the broken tooth fall harmlessly to the bottom of the gear case? Will the bull gear survive the broken gear or like many gears sets transfer damage? Folks do win the lottery against the odds. But the odds are against them and you.

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It may run forever but if a new tooth breaks off and gets between the gears it will break the case . Been there done that on other equipment.

Not my luck either, make it right when know its broken or pay the consequences when grenades.

The adjacent teeth to the one missing quite likely no longer have the strength in them to resist several more of them breaking off at once.
If were mine it would already be dismantled.

The only evidence (possibly) of the broken tooth is the intermittent rotational clunk i spoke of. if that is the source or the noise,its been like that for years now... the machine originally belonged to a neighbor of my father's and he borrowed it to demo his driveway almost 10 years ago and remembers it making the same noise. I am personally in favor of fixing the issue, My father (who's help I'd likely need to repair the gear) is of the opinion that its coming from the brake..maybe now that I found the tooth he will change his opinion.... part of the dilemma is that the "shop" is my backyard and though I have a well equipped garage, it's not large enough for the tractor. It is definitely a homeowner machine, but I do have some big plans and would like to see it running and fully functional. Looks like I'm going to give it a shot taking it apart. I'm assuming the shaft only comes out from one side or another and if memory serves it's likely from the left side (sitting in the seat) due to the ring gears engagement with the pinion. (I assume that would prevent the shaft moving the opposite way) now is the time to give me any of those useful tidbits as even removing a rear tire is likely going to be a project. I do have a very small homemade kubota b6000 backhoe loader to help, but if that tire weighs what I think it could, it may just be too much for it.

Removing a back tire is no big deal. Park it so that a hard surface (concrete, plywood,thick rubber mat, hard dirt) is under the tire and a couple of feet out to the side. Block it up so when the lug nuts are removed, the lug studs are centered in the holes. Lean the top of the tire toward you just enough to clear the studs. Grab the front and back of the tire and pull alternately so it walks toward you. Once you clear the hub, turn it and roll it away. The walking process is easy for one man, very hard for two.

Ooops !
I was typing the same thing and time that Mitch was. So, I just deleted the message.

Tinkerer, you ever tried walking a tire out when someone wants to "help" you?

anyone with any experience as far as what side to access from? ect..

mitch504 said:

Tinkerer, you ever tried walking a tire out when someone wants to "help" you?

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No I haven't Mitch.
I have wrestled tires by myself my entire life. As you know it isn't hard to do, if you go slow and keep it balanced upright.
I cannot imagine a two man scenario on a rear tire.
I was going to post earlier that if the tire gets off balance to let it go to the ground to prevent a back injury.
Also to use the backhoe to pick them up if they do go over.
I was 77 years old last year when I put new rear tires on my T/L/B. It was a piece of cake.