Front Differntial failure L3940

[jonsstihl]

do you road your tractor alot, the gear teeth look worn out. obviously a bearing has failed but the gears seem quite worn as well, perhaps lots of use coupled with a too low oil level. I don't think the front blower caused it specifically but do you run a counterweight while the blower is hooked up? It is a lot of weight up front.

 

[5030]

Kubota front axle assemblies don't contain a lot of fluid to begin with so it's imperative to check and maintain the fluid levels regularly. Looks pretty euchered to me but the housing looks ok. Surprised you didn't feel or hear it actually. Easy to check anyway, the center level plug and a single level plug on each outboard. Takes about 5 minutes total.

 

[jonsstihl]

our L40 series axle only has one level plug, close to the fill plug.

 

[5030]

our L40 series axle only has one level plug, close to the fill plug.

So do both my M9's but... each outboard has it's own fill and level plug as well. That may be different today as mine are pretty old units. In fact, om my M's the outboards are sealed with stationary seals from the axle proper and contain their own fluid

 

[sd455dan]

Some pictures

My 02 cents and I think this common across several brands of CUT's, that is that heavy loading of the front axle in 4x4 is causing stub axle inner or outer ball bearing stamped steel cage to wear / distort just enough to release ball bearing(s) at that point it is just a matter of time till the hard, high carbon chromium steel ball bearings find their way between gear teeth.

Then it gets ugly because the ball bearing is so much tougher than the average cast iron gear teeth, something has to give, so the real carnage begins.

In one of the pics a loose ball bearing is visible. If they look through the destroyed parts I would wager at least one mangled bearing cage will be found.
It sure seems like there should be ball bearings made with stronger tougher cages / larger shafts / larger bearings in general or the manufacturers should/could possibly be using roller bearings.
Not much a guy can do beyond checking/changing the oil often. I like to lift the front tires of the ground occasionally and check each side for any "New" play.

Op, I hope you are able to find a complete front axle at a reasonable price and for no further front axle problems in the future.

One thing is for sure you are not alone on this, it has happened to quite a few CUT owners of several different makes over the years.

 

[mikester]

My 02 cents and I think this common across several brands of CUT's, that is that heavy loading of the front axle in 4x4 is causing stub axle inner or outer ball bearing stamped steel cage to wear / distort just enough to release ball bearing(s) at that point it is just a matter of time till the hard, high carbon chromium steel ball bearings find their way between gear teeth.

4WD engaged, heavy front end loads, and sharp turns is all it takes to break a ring and pinion gear

I learned this expensive lesson on my old CUT. Ag equipment ISN'T construction equipment due to the lighter and less robust design

 

[sd455dan]

4WD engaged, heavy front end loads, and sharp turns is all it takes to break a ring and pinion gear

I learned this expensive lesson on my old CUT. Ag equipment ISN'T construction equipment due to the lighter and less robust design

That is another CUT design difference Very small diameter front 3rd member ring and pinion dimensions.
Some housings aren't even any larger in the center section than the outer axle tubes to house the center differential ring and pinion and spider gear. 50 HP running through very much miniaturized gear sets.
As you said, in 4x4, heavy FEL load, and a turn puts a lot of stress into the front drive and tractors do not have a transfer case (with differential action) in between the front and rear axle, so at least one front tire has to slip during a turn.

 

[5030]

One thing I don't care for as far as Kubota is concerned is they use ball bearings in the outboards. Large ag tractors use tapered roller bearings instead and I always worry about my M9's eating the outboard ball bearings and I keep an eye on the freeplay quite a bit. If the outboard bearings fail (cage or bearings), lifting the front axle and rocking the wheel assembly will tell you immediately if they have failed. Any rocking motion vertically or horizontally will immediately tell you if any internal failure has occured and not only the bearings but the though pin bushings as well. Usually when the pin bushings wear out (they are replaceable sintered sleeves, the outboards will start leaking as the lip seals aren't capable of retaining the gear oil.

I've replaced a few previously. You can do that yourself though it does take removing of the outboards completely but all it takes is a proper sized driver and new sleeves. Same applies to the front drive shaft coupler. I replace them as well. They are secured with a roll pin and are a designed wear point. The output shaft as well as the input pinion shaft is hardened and tempered and the coupler is soft. Using discretion for engaging 4wd and maintaining fluid levels and using gear oil instead of UDT or SUDT in the front axle is the way to go in my opinion.

My 2 cents for what it's worth.

 

[truckdiagnostics]

Using discretion for engaging 4wd and maintaining fluid levels and using gear oil instead of UDT or SUDT in the front axle is the way to go in my opinion.

Could you elaborate on the gear oil instead of the sudt. The stuff is stupid expensive. And from what i am hearing they are pretty straight forward to fix. And if they are failing for shock load issues, don't see where the expensive fluid is getting me anywhere. Chances are I am going to break something long before using sudt makes any sense.

 

[big bubba]

truckdiagonistics: you might consider using 75/90 full synthetic (GL5 as 5030 notes) esp given you're in a colder climate as well. valvoline is at the top of my list, what is your ft axle capacity? btw: if valvoline syn is to costly for you, they also make a conventional 75/90 as well that i use in my older truck... regards